Nickel-based active material precursor for lithium secondary battery, method of preparing the same, nickel-based active material for lithium secondary battery formed therefrom, and lithium secondary battery including positive electrode including nickel-based active material

ABSTRACT

A nickel-based active material precursor includes a particulate structure including a core portion, an intermediate layer portion on the core portion, and a shell portion on the intermediate layer portion, wherein the intermediate layer portion and the shell portion include primary particles radially arranged on the core portion, and each of the core portion and the intermediate layer portion includes a cation or anion different from that of the shell portion. The cation includes at least one selected from boron (B), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), titanium (Ti), vanadium (V), tungsten (W), chromium (Cr), iron (Fe), copper (Cu), zirconium (Zr), and aluminium (Al), and the anion includes at least one selected from phosphate (PO4), BO2, B4O7, B3O5, and F.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. patent application Ser. No.16/655,068, filed Oct. 16, 2019, which claims priority to and thebenefit of Korean Patent Application No. 10-2018-0123269, filed on Oct.16, 2018, in the Korean Intellectual Property Office, and Korean PatentApplication No. 10-2019-0127697, filed on Oct. 14, 2019, in the KoreanIntellectual Property Office, the entire content of all of which areincorporated herein by reference.

BACKGROUND 1. Field

One or more embodiments of the present disclosure relate to anickel-based active material precursor for a lithium secondary battery,a method of preparing the nickel-based active material precursor, anickel-based active material for a lithium secondary battery which isformed from the nickel-based active material precursor, and a lithiumsecondary battery including a positive electrode including thenickel-based active material.

2. Description of the Related Art

In line with the development of portable electronic devices,communication devices, and the like, there is an urgent need to developlithium secondary batteries with high energy density. In particular, toprovide a high energy density, lithium nickel manganese cobalt compositeoxides having a high nickel content have recently been widely used. Aspositive active materials of such lithium secondary batteries, a lithiumnickel manganese cobalt composite oxide, a lithium cobalt oxide, and/orthe like are being used. However, when these positive active materialsare used, cracks and crystal structural changes occur in primaryparticles as charging and discharging processes are repeated, and thus alithium secondary battery exhibits a deteriorated long-term lifespan,increased resistance, and unsatisfactory capacity characteristics, andtherefore, there is still a need for improvement.

SUMMARY

One or more aspects of the present disclosure are directed toward anickel-based active material precursor for a lithium secondary batterywhich exhibits a stable crystal structure due to enhanced bindingstrength between a transition metal of a nickel-based active materialand anions, and exhibits enhanced structural stability because problemsdue to cation mixing are addressed.

One or more aspects are directed toward a method of preparing theabove-described nickel-based active material precursor.

One or more aspects are directed toward a nickel-based active materialobtained from the above-described nickel-based active materialprecursor, and a lithium secondary battery exhibiting an enhancedlifespan due to the inclusion of a positive electrode including thenickel-based active material.

Additional aspects and embodiments will be set forth in part in thedescription which follows and, in part, will be apparent from thedescription, or may be learned by practice of the presented embodiments.

According to one or more embodiments, a nickel-based active materialprecursor for a lithium secondary battery includes a particulatestructure including a core portion, an intermediate layer portion on thecore portion, and a shell portion on the intermediate layer portion,wherein the intermediate layer portion and the shell portion includeprimary particles radially arranged on the core portion, and each of thecore portion and the intermediate layer portion includes a cation oranion different from that of the shell portion, wherein the cationincludes at least one selected from boron (B), magnesium (Mg), calcium(Ca), strontium (Sr), barium (Ba), titanium (Ti), vanadium (V), tungsten(W), chromium (Cr), iron (Fe), copper (Cu), zirconium (Zr), andaluminium (Al), and the anion includes at least one selected fromphosphate (PO₄), BO₂, B₄O₇, B₃O₅, and F.

According to one or more embodiments, a method of preparing anickel-based active material precursor for a lithium secondary batteryincludes a first process including a reaction among a complexing agent,a pH adjuster, metal raw materials for forming the nickel-based activematerial precursor, and a cation or anion-containing compound to form acore portion of the nickel-based active material precursor including acation or an anion; a second process of forming, on the core portionobtained by the first process, an intermediate layer portion containinga cation or an anion; and a third process of forming, on theintermediate layer portion obtained by the second process, a shellportion containing a cation or an anion, wherein each of the coreportion and the intermediate layer portion includes a cation or aniondifferent from that of the shell portion, wherein the cation includes atleast one selected from boron (B), magnesium (Mg), calcium (Ca),strontium (Sr), barium (Ba), titanium (Ti), vanadium (V), tungsten (W),chromium (Cr), iron (Fe), copper (Cu), zirconium (Zr), and aluminium(Al), and the anion includes at least one selected from phosphate (PO₄),BO₂, B₄O₇, B₃O₅, and F.

According to one or more embodiments, there is provided a nickel-basedactive material for a lithium secondary battery, the nickel-based activematerial being obtained from the nickel-based active material precursoraccording to the present embodiments.

According to one or more embodiments, a lithium secondary batteryincludes a positive electrode including the nickel-based active materialaccording to the present embodiments.

At least some of the above and other features of the invention are setout in the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The patent or application file contains at least one drawing executed incolor. Copies of this patent or patent application publication withcolor drawing(s) will be provided by the Office upon request and paymentof the necessary fee.

These and/or other aspects will become apparent and more readilyappreciated from the following description of the embodiments, taken inconjunction with the accompanying drawings in which:

FIG. 1A is a schematic partial perspective view of a nickel-based activematerial precursor according to an embodiment;

FIG. 1B is a more detailed partial perspective view of a nickel-basedactive material precursor according to an embodiment;

FIGS. 2A and 2B are scanning electron microscope (SEM) imagesrespectively showing cross-sections of nickel-based active materialsprepared according to Examples 1 and 2;

FIG. 2C is an SEM image showing a surface of the nickel-based activematerial of Example 2;

FIG. 2D is an SEM image showing the surface of the nickel-based activematerial of Example 2, at a resolution two times that of the image ofFIG. 2C;

FIGS. 3A and 3B are a high-angle annular dark-field scanningtransmission electron microscope (HAADF-STEM) image and anenergy-dispersive X-ray spectroscopy (EDS) image showing cross-sectionsof nickel-based active materials prepared according to Example 2 andComparative Example 2, respectively; and

FIG. 4 is a schematic view illustrating a structure of a lithiumsecondary battery according to an embodiment.

DETAILED DESCRIPTION

Reference will now be made in more detail to embodiments, examples ofwhich are illustrated in the accompanying drawings, wherein likereference numerals refer to like elements throughout. In this regard,the present embodiments may have different forms and should not beconstrued as being limited to the descriptions set forth herein.Accordingly, the embodiments are merely described below, by referring tothe figures, to explain aspects of the present description. As usedherein, the term “and/or” includes any and all combinations of one ormore of the associated listed items. Expressions such as “at least oneof,” “one of,” and “selected from,” when preceding a list of elements,modify the entire list of elements and do not modify the individualelements of the list. Further, the use of “may” when describingembodiments of the present invention refers to “one or more embodimentsof the present invention.”

Hereinafter, a nickel-based active material precursor for a lithiumsecondary battery, according to an embodiment of the present disclosure,a method of preparing the nickel-based active material precursor, anickel-based active material formed from the nickel-based activematerial precursor, and a lithium secondary battery including a positiveelectrode including the nickel-based active material will be describedin more detail. The following description is provided for illustrativepurposes only and is not intended to limit the scope of the presentdisclosure, and the present disclosure should be defined only by thescope of the following claims.

As used herein, the term “particulate structure” refers to a structurein the form of particles formed by agglomeration of a plurality ofprimary particles.

As used herein, the term “cation mixing” refers to an interchangebetween Li⁺ (0.76 Å) and Ni²⁺ (0.72 Å) which have a similar ionicradius, i.e., movement of Ni²⁺ ions to a lithium layer, thereby actingas a pillar of a layered structure. Such cation mixing blocks (orsubstantially reduces) lithium diffusion in the lithium layer, and thuscauses a local over-potential difference in the crystal structure,resulting in an increase in instability of the crystal structure.

As used herein, the term “porosity” refers to a ratio of an areaoccupied by pores to a total area. For example, the porosity of a shellportion is a ratio of an area occupied by pores to a total area of theshell portion. The same definition for “porosity” is also applied to acore portion and an intermediate layer portion. The porosity can becalculated, for example, as a ratio of the area occupied by the pores tothe total area of the core portion from the cross-sectional SEM image ofthe particulate structure.

As used herein, the term “radial center” refers to the center of aparticulate structure including a core portion, an intermediate layerportion including primary particles radially arranged on the coreportion, and a shell portion, as illustrated in FIGS. 1A and 1B.

As used herein, the term “radial” refers to a form arranged such thatmajor axes of primary particles included in the shell portion areperpendicular to a surface of the particulate structure or form an angleof ±30 degrees with respect to the perpendicular direction, asillustrated in FIGS. 1A and 1B.

As used herein, the term “mean particle diameter” refers to an averagediameter when particles are spherical, and an average diameter (orbreadth) of spheres of the same volume when the particles arenon-spherical. The mean particle diameter is the mean particle diameter(D50), which is defined as the particle diameter corresponding to thecumulative diameter distribution at 50%, which represents the particlediameter below which 50% of the sample lies. The mean particle diametermay be measured using a particle size analyzer (PSA).

As used herein, the term “irregular porous pores” refers to pores thatdo not have a regular pore size and shape and have no uniformity. Unlikethe shell portion, a core portion including irregular porous pores mayinclude atypical particles, and these atypical particles are irregularlyarranged, unlike the shell portion.

In the following drawings, like reference numerals denote like elements,and the size of each element in the drawings is exaggerated for clarityand convenience of explanation. In addition, embodiments set forthherein are provided for illustrative purposes only, and variousmodifications of these embodiments are possible. In addition, in a layerstructure, which will be described in more detail below, the expression“above” or “on” includes not only “directly on,” but also “being on”without contact between two elements.

A nickel-based active material precursor for a lithium secondarybattery, according to an embodiment, includes a particulate structureincluding a core portion (core), an intermediate layer portion(intermediate layer) on the core portion, and a shell portion (shell) onthe intermediate layer portion, in which the intermediate layer portionand the shell portion include primary particles radially arranged on thecore portion, and each of the core portion and the intermediate layerportion includes a cation and/or anion different from that of the shellportion, wherein the cation includes at least one selected from boron(B), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), titanium(Ti), vanadium (V), tungsten (W), chromium (Cr), iron (Fe), copper (Cu),zirconium (Zr), and aluminium (Al), and the anion includes at least oneselected from phosphate (PO₄), BO₂, B₄O₇, B₃O₅, and F.

Referring to FIGS. 1A and 1B, a nickel-based active material precursorfor a lithium secondary battery includes a particulate structure 100including a core portion 10, an intermediate layer portion 20 on thecore portion 10, and a shell portion 30 on the intermediate layerportion 20, in which the intermediate layer portion 20 and the shellportion 30 include primary particles 40 radially arranged on the coreportion 10, and the core portion 10 and the intermediate layer portion20, and the shell portion 30 include different cations and/or anions,wherein the cation includes at least one selected from B, Mg, Ca, Sr,Ba, Ti, V, W, Cr, Fe, Cu, Zr, and Al, and the anion includes at leastone selected from PO₄, BO₂, B₄O₇, B₃O₅, and F.

Referring to FIGS. 1A and 1B, the particulate structure 100 has astructure in which the core portion 10, the intermediate layer portion20, and the shell portion 30 are sequentially stacked. The particulatestructure 100 is, for example, a secondary particle. The core portion10, which is a porous core portion, reduces a lithium diffusion distancein a nickel-based active material obtained from the nickel-based activematerial precursor. The intermediate layer portion 20 has a high densitydue to radial arrangement of the primary particles 40. In the shellportion 30, the primary particles 40 are also radially arranged. In theparticulate structure 100, the primary particles 40 are radiallyarranged on the core portion 10 to form the intermediate layer portion20 and/or the shell portion 30, such that stress applied to the primaryparticles 40 during charging and discharging is reduced. Accordingly,volume changes of the primary particles 40 are effectively (suitably)accommodated. Thus, cracks due to a volume change of a nickel-basedactive material prepared from the nickel-based active material precursorduring charging and discharging are suppressed or reduced. In one ormore embodiments, each of the core portion 10 and the intermediate layerportion 20 includes cations and/or anions different from that of theshell portion 30.

The cations are, for example, metal cations having an ionic radiussimilar to but different from that of nickel cations and/or having anincreased binding affinity with oxygen. Since the core portion 10, theintermediate layer portion 20, and/or the shell portion 30 include(s)these metal cations, cation mixing is suppressed (or reduced) in thecrystal lattice, resulting in suppression (or reduction) of the elutionof nickel ions, and accordingly, the structural stability of a portionincluding the cations is enhanced. For example, metal cations having anionic radius similar to but different from that of nickel cations aresubstituted or doped in lithium cation sites or vacancies of the crystallattice, thereby partially blocking the transfer path of Ni²⁺ in thelithium layer or preventing the transfer of Ni²⁺ by repulsion, thusresulting in reduced cation mixing. In addition, because the shellportion 30 includes such metal cations, a transition metal layer isstabilized, and thus the volume change of crystals due to charging anddischarging and the transfer of nickel cations are suppressed (orreduced), thus resulting in suppressed (or reduced) cation mixing. Inaddition, the generation of a NiO phase (a rock salt phase) on a surfaceduring synthesis of a positive active material is suppressed or reduced,and deintercalation of oxygen is suppressed or reduced, and thus thepositive active material becomes more stable.

The anions are, for example, anions having a higher electronegativitythan oxygen. Since the core portion 10, the intermediate layer portion20, and/or the shell portion 30 include(s) anions having such highelectronegativity, binding strength between the transition metal and theanions in the crystal lattice is enhanced. When the binding strengthbetween the transition metal and the anions is increased, a structuralchange of the active material and consequent deintercalation of oxygenare suppressed or reduced, and accordingly, the structural stability ofthe positive active material is enhanced. For example, the instabilityof an anion layer due to lithium entry during charging and dischargingis reduced, and gas generation due to oxygen release is suppressed orreduced. Accordingly, a nickel-based active material prepared from suchnickel-based active material precursor exhibits both a high dischargecapacity and excellent (or suitable) structural stability.

Referring to FIGS. 1A and 1B, the shell portion 30 includes, forexample, at least one cation selected from B, Mg, Ca, Sr, Ba, Ti, V, W,Cr, Fe, Cu, Zr, and Al. The amount of the cation(s) included in thenickel-based active material precursor is, for example, 0.9 mol % orless, 0.7 mol % or less, 0.5 mol % or less, 0.3 mol % or less, or 0.28mol % or less with respect to a total amount of the nickel-based activematerial precursor. For example, the amount of the cation(s) included inthe nickel-based active material precursor is in a range of about 0.0001mol % to about 0.9 mol %, about 0.001 mol % to about 0.7 mol %, about0.001 mol % to about 0.5 mol %, about 0.001 mol % to about 0.3 mol %, orabout 0.001 mol % to about 0.28 mol % with respect to the total amountof the nickel-based active material precursor. When the amount of thecation(s) is too large, doping in the shell portion is difficult suchthat the amount of impurities increases, and the porosity of the shellportion is further increased. Accordingly, a lithium battery including anickel-based active material obtained from such a porous nickel-basedactive material precursor exhibits reduced volume capacity anddeteriorated cycle characteristics.

Referring to FIGS. 1A and 1B, the core portion 10 and the intermediatelayer portion 20 include, for example, at least one anion selected fromPO₄, BO₂, B₄O₇, B₃O₅, and F. The amount of the anions included in thenickel-based active material precursor is, for example, 0.06 mol % orless, 0.05 mol % or less, 0.04 mol % or less, or 0.03 mol % or less withrespect to the total amount of the nickel-based active materialprecursor. The amount of the anions included in the nickel-based activematerial precursor is in a range of, for example, about 0.0001 mol % toabout 0.06 mol %, about 0.001 mol % to about 0.05 mol %, about 0.005 mol% to about 0.04 mol %, or about 0.01 mol % to about 0.03 mol % withrespect to the total amount of the nickel-based active materialprecursor.

The amount of the cation(s) included in the shell portion 30 of thenickel-based active material precursor is, for example, 2.0 mol % orless, 1.8 mol % or less, 1.6 mol % or less, 1.4 mol % or less, 1.33 mol% or less, or 0.41 mol % or less with respect to the total amount of theshell portion 30. For example, the amount of the cation(s) included inthe shell portion 30 of the nickel-based active material precursor is ina range of about 0.0001 mol % to about 2.0 mol %, about 0.001 mol % toabout 1.8 mol %, about 0.001 mol % to about 1.6 mol %, about 0.001 mol %to about 1.4 mol %, about 0.001 mol % to about 1.33 mol %, or about0.001 mol % to about 0.41 mol % with respect to the total amount of theshell portion 30.

A total amount of the anions included in the core portion 10 and theintermediate layer portion 20 of the nickel-based active materialprecursor is, for example, 1.0 mol % or less, 0.8 mol % or less, 0.6 mol% or less, 0.4 mol % or less, or 0.18 mol % or less with respect to atotal amount of the core portion 10 and the intermediate layer portion20. The total amount of the anions included in the core portion 10 andthe intermediate layer portion 20 of the nickel-based active materialprecursor is in a range of about 0.0001 mol % to about 1.0 mol %, about0.001 mol % to about 0.8 mol %, about 0.001 mol % to about 0.6 mol %,about 0.001 mol % to about 0.4 mol %, or about 0.001 mol % to 0.18 mol %with respect to the total amount of the core portion 10 and theintermediate layer portion 20.

Because the whole nickel-based active material precursor, the coreportion 10 of the nickel-based active material precursor, theintermediate layer portion 20 of the nickel-based active materialprecursor, and/or the shell portion 30 of the nickel-based activematerial precursor include cations and/or anions within theabove-described amount ranges, the structural stability of anickel-based active material prepared from the nickel-based activematerial precursor is further enhanced.

Referring to FIGS. 1A and 1B, in the particulate structure 100, a firstpore distribution is formed such that the core portion 10 has a higherporosity than that of the intermediate layer portion 20 and the shellportion 30, or a second pore distribution is formed such that the coreportion 10 and the shell portion 30 have a higher porosity than that ofthe intermediate layer portion 20.

A nickel-based active material precursor having the first poredistribution will now be described in more detail.

FIG. 2A is an image showing the cross-section of a nickel-based activematerial that is prepared from a nickel-based active material precursorhaving the first pore distribution and has substantially the same poredistribution as that of the nickel-based active material precursorhaving the first pore distribution.

Referring to FIGS. 1A and 1B, for example, the porosity of theintermediate layer portion 20 and the shell portion 30 is lower than theporosity of the core portion 10, which is porous. Thus, the intermediatelayer portion 20 and the shell portion 30 have a higher density thanthat of the core portion 10, which is porous. When the particulatestructure 100 has such a density gradient, a surface area where lithiumdiffusion occurs is increased and diffusion is facilitated, and thus anickel-based active material prepared from the nickel-based activematerial precursor exhibits enhanced rate capability during charging anddischarging. In addition, a lithium secondary battery including suchnickel-based active material exhibits enhanced lifespan characteristics.For example, the porosity of the core portion 10, the intermediate layerportion 20, and the shell portion 30 may be sequentially reduced.

Referring to FIGS. 1A and 1B, the shell portion 30 forms open pores bycontrolling the density thereof, and an electrolytic solution permeatesthrough the open pores, thereby increasing a diffusion coefficient oflithium ions. Since the particulate structure 100 includes the shellportion 30 having such an increased diffusion coefficient, a surfacearea where lithium diffusion occurs is increased and diffusion isfacilitated, and thus a nickel-based active material prepared from thenickel-based active material precursor exhibits enhanced rate capabilityduring charging and discharging. In addition, a lithium secondarybattery including such nickel-based active material exhibits enhancedlifespan characteristics.

Referring to FIGS. 1A and 1B, the core portion 10 is a regioncorresponding to, from the center of the particulate structure 100, 40length % to 70 length % of a total distance between the center and theoutermost surface of the particulate structure 100. In some embodiments,the core portion 10 refers to the remaining region excluding a regionwithin, for example, 3 μm from the surface of the particulate structure100. The core portion 10 has a thickness (when measured from the center)of, for example, about 2 μm to about 5 μm, for example, about 2.5 μm toabout 3.5 μm. The core portion 10 has a porosity of, for example, about15% to about 20%. The pore size of the core portion 10 may be greaterthan the pore size of the shell portion 30 which will be describedbelow, and may be in a range of about 150 nm to about 1 μm, for example,about 150 nm to about 550 nm, for example, about 200 nm to about 500 nm.The volume of the core portion 10 is, for example, 15% or less or 10% orless of a total volume of the particulate structure 100. When the coreportion 10 has such region, porosity, volume, and/or pore size, thestructural stability of a nickel-based active material prepared from thenickel-based active material precursor is further enhanced.

Referring to FIGS. 1A and 1B, the shell portion 30 is a regioncorresponding to, from the outermost surface of the particulatestructure 100, 5 length % to 20 length % of a total distance between thecenter and the outermost surface of the particulate structure 100. Insome embodiments, the shell portion 30 refers to an area within, forexample, 2 μm from the outermost surface of the particulate structure100. The shell portion 30 has a thickness of about 1 μm to about 3 μm,for example, about 1.5 μm to about 2 μm. The porosity of the shellportion 30 is, for example, 5% or less, 2% or less, for example, in arange of about 0.1% to about 2%. The pore size of the shell portion 30is less than 150 nm, for example, 100 nm or less, for example, in arange of about 20 nm to about 90 nm. The volume of the shell portion 30is, for example, 50% or more, 60% or more, or 70% or more of the totalvolume of the particulate structure 100. The volume of the shell portion30 is in a range of, for example, about 50% to about 80%, or about 60%to 75% of the total volume of the particulate structure 100. When theshell portion 30 has such region, porosity, volume, and/or pore size,the structural stability of a nickel-based active material prepared fromthe nickel-based active material precursor is further enhanced.

Referring to FIGS. 1A and 1B, the intermediate layer portion 20 is theremaining area except for the core portion 10 and the shell portion 30.The intermediate layer portion 20 has a thickness of about 1 μm to about3 μm, for example, about 1.4 μm to about 2 μm. The porosity of theintermediate layer portion 20 is in a range of, for example, about 0.1%to about 14.8%, about 2% to about 14.8%, about 5% to about 14.8%, orabout 10% to about 14.8%. The pore size of the intermediate layerportion 20 is less than 150 nm, for example, 100 nm or less, forexample, in a range of about 20 nm to about 90 nm. The volume of theintermediate layer portion 20 is in a range of, for example, about 20%to about 35% of the total volume of the particulate structure 100. Whenthe intermediate layer portion 20 has such region, porosity, volume,and/or pore size, the structural stability of a nickel-based activematerial prepared from the nickel-based active material precursor isfurther enhanced.

A nickel-based active material precursor having the second poredistribution will now be described in more detail.

FIGS. 2B and 3A are images showing the cross-section of a nickel-basedactive material prepared from a nickel-based active material precursorhaving the second pore distribution and having substantially the samepore distribution as that of the nickel-based active material precursorhaving the second pore distribution.

Referring to FIGS. 1A and 1B, in the particulate structure 100 havingthe second pore distribution, for example, the porosity of each of thecore portion 10 and the shell portion 30 is higher than that of theintermediate layer portion 20. Thus, the core portion 10 and the shellportion 30 each have a lower density than that of the intermediate layerportion 20. When the particulate structure 100 has such densitygradient, a surface area where lithium diffusion occurs is increased anddiffusion is facilitated, and thus the nickel-based active materialprepared from the nickel-based active material precursor exhibitsenhanced rate capability during charging and discharging. In addition, alithium secondary battery including such nickel-based active materialexhibits enhanced lifespan characteristics.

Referring to FIGS. 1A and 1B, the shell portion 30 of the nickel-basedactive material precursor having the second pore distribution is an area(and/or volume) corresponding to, from the outermost surface of theparticulate structure 100, 5 length % to 20 length % of a total distancebetween the center and outermost surface of the particulate structure100. In some embodiments, the shell portion 30 refers to an area (and/orvolume) within, for example, 2 μm from the outermost surface of theparticulate structure 100. The shell portion 30 has a thickness of, forexample, about 1 μm to about 3 μm, for example, about 1.5 μm to about 2μm. The shell portion 30 has a porosity of, for example, about 15% toabout 20%. The pore size of the shell portion 30 is in a range of about150 nm to about 1 μm, for example, about 150 nm to about 550 nm, forexample, about 200 nm to about 500 nm. The volume of the shell portion30 is, for example, 50% or more, 60% or more, or 70% or more of thetotal volume of the particulate structure 100. The volume of the shellportion 30 is in a range of, for example, about 50% to about 80%, orabout 60% to about 75% of the total volume of the particulate structure100. When the shell portion 30 has such structure, porosity, and/or poresize, the structural stability of a nickel-based active materialprepared from the nickel-based active material precursor is furtherenhanced.

The core portion 10 and the intermediate layer portion 20 of thenickel-based active material precursor having the second poredistribution have the same configurations as those of the core portion10 and the intermediate layer portion 20 of the above-describednickel-based active material precursor having the first poredistribution.

Referring to FIGS. 1A, 1B, and 2B, the primary particles 40 are radiallyarranged in the shell portion 30, and thus pores are formed between theradially arranged primary particles 40, and these pores are alsoradially arranged, thereby forming open pores extending from the insideof a precursor particle to the surface of the precursor particle. Byincluding the open pores in the shell portion 30, entry and exit oflithium ions to and from a nickel-based active material prepared fromthe nickel-based active material precursor are further facilitated, andthus a lithium battery including the nickel-based active materialexhibits enhanced rate capability.

Referring to FIGS. 1A and 1B, a secondary particle included in thenickel-based active material precursor may be in the form of a singleparticulate structure 100. The secondary particles may have a meanparticle diameter of, for example, about 5 μm to about 25 μm, or about 9μm to about 20 μm. When the secondary particles have a mean particlediameter within the above-described range, the structural stability of anickel-based active material prepared from the nickel-based activematerial precursor is further enhanced.

Referring to FIG. 1B, in an example embodiment, the primary particle 40is a non-spherical particle having a minor axis and a major axis. Theminor axis is an axis connecting points having the smallest distancebetween opposite ends of the primary particle 40, and the major axis isan axis connecting points having the greatest distance between oppositeends of the primary particle 40. A ratio of the minor axis to the majoraxis of the primary particle 40 is in a range of, for example, about 1:2to about 1:20, about 1:3 to about 1:20, or about 1:5 to about 1:15. Whenthe primary particle 40 has a ratio of the minor axis to the major axiswithin the above-described range, use of lithium ions in a nickel-basedactive material obtained from the nickel-based active material precursoris further facilitated.

Referring to FIG. 1B, the primary particles 40, which are non-sphericalparticles, include, for example, plate particles. Plate particles areparticles having two opposing surfaces, wherein a surface length(length) is larger than a thickness (which is a distance between the twosurfaces). The surface length of the plate particles is the larger ofthe two dimensions (e.g., length and width) defining the surface. Thetwo dimensions defining the surface can be different from or identicalto each other, and are each larger than the thickness. The thickness ofthe plate particle is the length of the minor axis, and the surfacelength of the plate particle is the length of the major axis. Thesurfaces of the plate particles may each be in the form of a polygonsuch as a trigon, a tetragon, a pentagon, a hexagon, or the like, acircular shape, or an oval shape, but are not limited thereto, and thesurfaces of the plate particles may have any suitable form. Examples ofthe plate particles include nanodiscs, tetragonal nanosheets, pentagonalnanosheets, and hexagonal nanosheets, without limitation. Particularforms of the plate particles vary depending on specific conditions underwhich secondary particles are prepared. The two opposing surfaces of theplate particle may not be parallel to each other, an angle between asurface and a side surface may be variously changed, edges of thesurface and the side surface may have a rounded shape, and each of thesurface and the side surface may have a planar or curved shape. Themajor axes 41 of the plate particles are radially arranged on the coreportion 10 of the particulate structure 100, thereby forming theintermediate layer portion 20 and/or the shell portion 30. A lengthratio of the minor axis to the major axis of the plate particle is in arange of, for example, about 1:2 to about 1:20, about 1:3 to about 1:20,or about 1:5 to about 1:15. In an example embodiment, the plateparticles each have an average thickness of about 100 nm to about 250nm, or about 100 nm to about 200 nm, and have an average surface lengthof about 250 nm to about 1,100 nm, or about 300 nm to about 1,000 nm.The average surface length of the plate particles is 2 times to 10 timesthe particle's average thickness. When the plate particles havethickness, average surface length, and a ratio thereof within theabove-described ranges, radial arrangement of the plate particles on aporous core portion is more suitably facilitated and consequently, thestructural stability of a nickel-based active material obtained from thenickel-based active material precursor is further enhanced.

Referring to FIGS. 1A and 1B, secondary particles in the form of theparticulate structure 100 included in the nickel-based active materialprecursor have a specific surface area of about 4 m²/g to about 10 m²/g.The specific surface area may be measured by a BET method. For example,a BET 6-point method may be used according to a nitrogen gas adsorptionmethod by using a porosimetry analyzer (Belsorp-II Mini, Bell JapanInc.). When the nickel-based active material precursor has a relativelylarge specific surface area within the above range, diffusion of lithiumions in a nickel-based active material prepared from the nickel-basedactive material precursor is more facilitated.

The nickel-based active material precursor is, for example, a compoundrepresented by Formula 1 or 2 below:

Ni_(1-x-y-z)Co_(x)Mn_(y)M_(z)(OH)_(2-α)X_(α)  Formula 1

Ni_(1-x-y-z)Co_(x)Al_(y)M_(z)(OH)_(2-α)X_(α),  Formula 2

wherein, in Formula 1 and 2, M is an element selected from B, Mg, Ca,Sr, Ba, Ti, V, W, Cr, Fe, Cu, Zr, and Al, x≤(1-x-y-z), y≤(1-x-y-z),0<x<1, 0≤y<1, 0<z≤0.01, and 0<α≤0.01, and X is at least one selectedfrom PO₄, BO₂, B₄O₇, B₃O₅, and F. In Formula 1, for example, 0<x≤0.33,0≤y≤0.5, 0<z≤0.01, 0.33≤(1-x-y-z)≤0.97, and 0<α≤0.01. In Formula 1, forexample, 0<x≤0.33, 0<y≤0.33, 0<z≤0.009, 0.33≤(1-x-y-z)≤0.97, and0<α≤0.0013. The content of nickel in the nickel-based active materialprecursor may be in a range of, for example, about 33 mol % to about 97mol %, about 33 mol % to about 95 mol %, for example, about 50 mol % toabout 90 mol %, for example, about 60 mol % to about 85 mol %, withrespect to a total amount of transition metals. The total amount oftransition metals refers to a total amount of nickel, cobalt, andmanganese in Formula 1 and a total amount of nickel, cobalt, andaluminium in Formula 2.

The content of nickel in the nickel-based active material precursor mayrange from about 33 mol % to about 97 mol % with respect to the totalamount of transition metals, and may be higher than the content ofmanganese and the content of cobalt.

The metal hydroxide of Formulae 1 or 2 is, for example,(Ni_(0.6)Co_(0.2)Mn_(0.2))_(1-a)M_(a)(OH)_(2-α)X_(α),(Ni_(0.5)Co_(0.2)Mn_(0.3))_(1-a)M_(a)(OH)_(2-α)X_(α),(Ni_(0.7)Co_(0.15)Mn_(0.15))_(1-a)M_(a)(OH)_(2-α)X_(α),(Ni_(0.85)Co_(0.1)Al_(0.05))_(1-a)M_(a)(OH)_(2-α)X_(α), or(Ni_(0.91)Co_(0.06)Mn_(0.03))_(1-a)M_(a)(OH)_(2-α)X_(α), wherein0<a<0.01 and 0<α≤0.01, M is at least one element selected from B, Mg,Ca, Sr, Ba, Ti, V, W, Cr, Fe, Cu, Zr, and Al, and X is at least oneselected from PO₄, BO₂, B₄O₇, B₃O₅, and F. For example, 0<a<0.009 and0<α≤0.0013.

A method of preparing a nickel-based active material precursor,according to an embodiment, includes: a first process of allowing areaction to occur among a complexing agent, a pH adjuster, metal rawmaterials for forming a nickel-based active material precursor, and acation or anion-containing compound to form a core portion of anickel-based active material precursor including a cation and/or ananion; a second process of forming, on the core portion obtained by thefirst process, an intermediate layer portion containing a cation or ananion; and a third process of forming, on the intermediate layer portionobtained by the second process, a shell portion containing a cation oran anion, wherein each of the core portion and the intermediate layerportion includes a cation or anion different from that of the shellportion, the cation includes at least one selected from B, Mg, Ca, Sr,Ba, Ti, V, W, Cr, Fe, Cu, Zr and Al, and the anion includes at least oneselected from PO₄, BO₂, B₄O₇, B₃O₅, and F.

In the first, second and third processes, a reaction temperature is in arange of about 40° C. to about 60° C., a stirring power is in a range ofabout 0.1 kW/m³ to about 6.0 kW/m³, pH ranges from about 10 to about 12,and the amount of the complexing agent included in the reaction mixtureis in a range of about 0.1 M to about 0.6 M, for example, about 0.3 M toabout 0.6 M. Within the above-described ranges, a nickel-based activematerial precursor that more satisfactorily (suitably) matches theabove-described structure may be obtained.

The feed rate of the metal raw materials is higher in the second processthan in the first process, and the feed rate of the metal raw materialsin the third process may be maintained at the same level as that in thefirst process. That is, the feed rate of the metal raw materials in thefirst process may be the same as that of the metal raw materials in thethird process, and the feed rate of the metal raw materials in thesecond process may be greater than in the first and third processes. Forexample, the feed rate of the metal raw materials in the second processmay be increased to 10% to 50% based on the feed rate in the firstprocess, and the feed rate of the metal raw materials in the thirdprocess may be the same as that in the first process. As such, byadjusting the feed rate of the metal raw materials, a nickel-basedactive material precursor that more satisfactorily (suitably) matchesthe above-described structure may be obtained.

The stirring power of the first process is the highest, and the stirringpower of the third process is the lowest, and the stirring power of thesecond process may have a stirring power of a level between the stirringpower of the first process and the stirring power of the third process.When the core portion and the intermediate layer portion include cationsand/or anions different from those of the shell portion, a nickel-basedactive material precursor having the above-described novel structure isobtained. For example, the stirring power of the reaction mixture in areactor may be lower in the second process than in the first process,and the stirring power of the reaction mixture in a reactor may be lowerin the third process than in the second process. The stirring power ofthe first process may be in a range of about 1 kW/m³ to about 4 kW/m²,the stirring power of the second process may be in a range of about 1kW/m³ to about 3 kW/m³, and the stirring power of the third process maybe in a range of about 1 kW/m³ to about 2 kW/m³. The stirring power ofthe first process, the second process, and the third process may besequentially reduced, thereby obtaining a nickel-based active materialprecursor that more satisfactorily (suitably) matches theabove-described structure. In addition, in the precursor preparationmethod, the stirring rate of the reaction mixture in a reactor in thefirst process, the second process, and the third process may besequentially reduced. As such, by a sequential reduction in the stirringrates of the first, second and third processes, a nickel-based activematerial precursor that more satisfactorily (suitably) matches theabove-described structure may be obtained.

The pH of the reaction mixture of the second process may be the same asthat of the reaction mixture of the third process, and the pH of thereaction mixture of each of the second and third processes may be lowerthan that of the reaction mixture of the first process. For example, thepH of the reaction mixture in the second and third processes may beabout 0.5 to about 1.6, about 1.1 to about 1.6, or about 1.2 to about1.5 less than that of the reaction mixture of the first process at areaction temperature of 50° C. In one or more embodiments, as the firstprocess, the second process, and the third process proceed, the pH ofthe reaction mixture in a reactor may be sequentially reduced. Forexample, the pH of the reaction mixture of the second process may beabout 0.55 to about 0.85 lower than that of the reaction mixture of thefirst process at a reaction temperature of 50° C., and the pH of thereaction mixture of the third process may be about 0.35 to about 0.55lower than that of the reaction mixture of the second process. In one ormore embodiments, as the first process, the second process, and thethird process proceed, the pH of the reaction mixture in a reactor maybe maintained at the same level. For example, the pH of the reactionmixture of the first to third processes may be in a range of about 10 toabout 11.5 at a reaction temperature of 50° C. As such, by adjusting thepH of the reaction mixture according to the present embodiments, anickel-based active material precursor that more satisfactorily(suitably) matches the above-described structure may be obtained.

The concentration of the complexing agent may be sequentially increasedas the first process, the second process, and the third process proceed.For example, the concentration of the complexing agent included in thereaction mixture of the second process may be increased compared to thatof the complexing agent included in the reaction mixture of the firstprocess, and the concentration of the complexing agent included in thereaction mixture of the third process may be increased compared to thatof the complexing agent included in the reaction mixture of the secondprocess. For example, the concentration of the complexing agent includedin the reaction mixture of the second process may be increased by about0.05 M to about 0.5 M compared to that of the complexing agent includedin the reaction mixture of the first process, and the concentration ofthe complexing agent included in the reaction mixture of the thirdprocess may be increased by about 0.05 M to about 0.5 M compared to thatof the complexing agent included in the reaction mixture of the secondprocess. In one or more embodiments, as the first process, the secondprocess, and the third process proceed, the concentration of thecomplexing agent included in the reaction mixture may be maintained atthe same level. For example, the concentration of the complexing agentincluded in the reaction mixture of each of the first to third processesmay be in a range of about 0.5 M to about 0.6 M.

In the first process, a complexing agent, a pH adjuster, metal rawmaterials for forming the nickel-based active material precursor, and acation or anion-containing compound are allowed to react to form andgrow a core portion of the nickel-based active material precursorcontaining the cation and/or anion. In the first process, a growth rateof precursor seed particles may be about 0.32±0.05 μm/hr. In the firstprocess, the stirring power of the reaction mixture may be in a range ofabout 1.2 kW/m³ to about 4 kW/m³, for example, 3.0 kW/m³, and the pH ofthe reaction mixture may be in a range of about 10.5 to about 12. Forexample, in the first process, the feed rate of the metal raw materialsmay be in a range of about 1.0 ml/min to about 10.0 ml/min, for example,4.3 ml/min, and the feed rate of the complexing agent may be about 0.1to about 0.6 times, for example, 0.15 times a molar feed rate of themetal raw materials. For example, in the first process, the feed rate ofthe cation-containing compound or the anion-containing compound is in arange of about 1.0 ml/min to about 3.0 ml/min, for example, 1.6 ml/min.The temperature of the reaction mixture is in a range of, for example,40° C. to 60° C., for example, 50° C., and the reaction mixture has a pHof about 11 to about 12, for example, about 11.0 to about 11.5.

In the second process, reaction conditions are changed and anintermediate layer portion containing a cation or an anion is formed andgrown on the core portion using a cation or anion-containing compound.In the second process, a precursor seed has the same growth rate or agrowth rate increased by 20% or greater, compared to that of a precursorseed of the first process. The feed rate of the metal raw materials inthe second process may be 1.2 times or more, for example, about 1.2times to about 2.5 times that of the metal raw materials of the firstprocess, and the concentration of the complexing agent in the reactionmixture may be 0.05 M or more, for example, about 0.05 M to about 0.15 Mhigher than that of the complexing agent in the first process. In thesecond process, the stirring power of the reaction mixture may be in arange of about 1 kW/m³ to about 3 kW/m³, for example, 2.5 kW/m³, and thereaction mixture may have a pH of about 10 to about 11. For example, inthe second process, the concentration of the complexing agent is in arange of, for example, about 0.3 M to about 0.55 M, the feed rate of themetal raw materials is in a range of about 1 ml/min to about 10 ml/min,and the feed rate of the complexing agent is in a range of about 0.1ml/min to about 2 ml/min. For example, the feed rate of thecation-containing compound or the anion-containing compound in thesecond process is in a range of about 1.0 ml/min to about 3.0 ml/min,for example, 2.0 ml/min.

In the third process, reaction conditions are changed and a shellportion containing a cation or an anion is formed and grown on theintermediate layer portion obtained by the second process, using acation or anion-containing compound, thereby obtaining a nickel-basedactive material precursor for a lithium secondary battery. When the meanparticle diameter (D50) of precursor particles in the second processreaches about 9 μm to about 12 μm, for example, about 12 μm, the thirdprocess proceeds. As compared to the growth rate of the precursorparticles in the second process, the growth rate of the precursorparticles in the third process may be increased by 2 times or more, forexample, 3 times or more. To this end, the reaction product in areactor, having gone through the second process, may be partiallyremoved to dilute the concentration of the reaction product in thereactor. The product removed from the inside of the reactor may be usedin another reactor. The feed rate of the metal raw materials in thethird process may be 0.5 times or more, for example, about 0.5 times toabout 0.9 times that of the metal raw materials of the second process,and the concentration of the complexing agent in the reaction mixturemay be higher by 0.05 M or more, for example, about 0.05 M to about 0.15M, as compared to that of the complexing agent in the second process. Inthe third process, the precipitate is grown to thereby obtain anickel-based active material precursor. In the third process, thestirring power of the reaction mixture may be in a range of about 1kW/m³ to about 3 kW/m³, for example, 2.0 kW/m³, and the reaction mixturemay have a pH of about 10 to about 11. For example, in the thirdprocess, the concentration of the complexing agent is in a range of, forexample, about 0.3 M to about 0.6 M, the feed rate of the metal rawmaterials is in a range of about 2 ml/min to about 10 ml/min, and thefeed rate of the complexing agent is in a range of about 0.1 ml/min toabout 2 ml/min. For example, the feed rate of the cation-containingcompound or the anion-containing compound in the third process is in arange of about 1.0 ml/min to about 3.0 ml/min, for example, 1.6 ml/min.

In the precursor preparation method, by considering the composition ofthe nickel-based active material precursor, metal precursorscorresponding to the nickel-based active material precursor may be usedas metal raw materials. Examples of metal raw materials include, but arenot limited to, metal carbonates, metal sulfates, metal nitrates, metalchlorides, metal fluorides, and the like, and any suitable metalprecursor may be used. For example, as a Ni-containing compound, atleast one selected from nickel sulfate, nickel nitrate, nickel chloride,and nickel fluoride may be used. For example, as a Co-containingcompound, at least one selected from cobalt sulfate, cobalt nitrate,cobalt chloride, and cobalt fluoride may be used. For example, as aMn-containing compound, at least one selected from manganese sulfate,manganese nitrate, manganese chloride, and manganese fluoride may beused. For example, an Al-containing compound, at least one selected fromaluminium sulfate, aluminium nitrate, aluminium chloride, and aluminiumfluoride may be used. For example, as a metal (M)-containing compound,at least one selected from a sulfate, a nitrate, a chloride salt, and afluoride salt of the metal (M) may be used.

To control the growth rate of nickel-based active material precursorparticles, the feed rate of metal raw materials for growing theparticles may be increased by about 15% to about 35%, for example, about25% in the second process, as compared to the first process, and may bereduced by about 20% to about 35%, for example, about 33% in the thirdprocess, as compared to the second process. In addition, the feed rateof the complexing agent such as ammonia water in the second process maybe increased by about 10% to about 30%, for example, about 20% withrespect to the feed rate of the complexing agent such as ammonia waterin the first process, thereby increasing the density of the particles.

The concentration of the cation-containing compound or theanion-containing compound may be adjusted such that the content ofcations or anions in the nickel-based active material precursor, whichis the resulting product, is in a range of about 0.01 mol % to about 1.0mol %. According to one or more embodiments, the anion-containingcompound is used in forming a core and an intermediate layer, and thecation-containing compound is used in forming a shell.

As the cation-containing compound, a cation-containing salt or base suchas a chloride, a sulfate, an oxalate, a carbonate, a hydroxide, a halideand/or the like that contains at least one selected from B, Mg, Ca, Sr,Ba, Ti, V, W, Cr, Fe, Cu, Zr, and Al may be used. In some embodiments, acation-containing oxide may be used. For example, tungsten oxide (WO₂)and/or the like may be used.

As the anion-containing compound, a phosphate, an oxide, and/or the likethat contains at least one selected from PO₄, BO₂, B₄O₇, B₃O₅, and F maybe used. For example, monosodium phosphate (NaH₂PO₄), disodium phosphate(Na₂HPO₄), and/or the like may be used.

The pH adjuster serves to lower the solubility of metal ions inside areactor to precipitate the metal ions as hydroxides. The pH adjuster is,for example, sodium hydroxide (NaOH), sodium carbonate (Na₂CO₃), and/orthe like. The pH adjuster is, for example, NaOH.

The complexing agent controls the forming reaction rate of a precipitatein a co-precipitation reaction. The complexing agent may be ammoniumhydroxide (NH₄OH)(ammonia water), citric acid, acrylic acid, tartaricacid, glycolic acid, and/or the like. The amount of the complexing agentis used at a general (e.g., at any suitable) level. The complexing agentis, for example, ammonia water.

A nickel-based active material according to one or more embodiments isobtained from the above-described nickel-based active materialprecursor. The nickel-based active material is, for example, a compoundrepresented by Formula 3 or 4:

Li_(a)(Ni_(1-x-y-z)Co_(x)Mn_(y)M_(z))O_(2-α)X_(α)  Formula 3

Li_(a)(N_(1-x-y-z)Co_(x)Al_(y)M_(z))O_(2-α)X_(α),  Formula 4

wherein, in Formulae 3 and 4, M is an element selected from B, Mg, Ca,Sr, Ba, Ti, V, Cr, Fe, Cu, Zr, and Al, 0.95≤a≤1.3, x≤(1-x-y-z),y≤(1-x-y-z), 0<x<1, 0<y<1, 0<z≤0.01, and 0<α≤0.01, and X is at least oneselected from PO₄, BO₂, B₄O₇, B₃O₅, and F. As such, in the nickel-basedactive material of Formula 3 or 4, the content of Ni is greater thanthat of Co and greater than the content of Mn or Al.

In Formulae 3 and 4, 0.95a1.3, for example, 1.0≤a≤1.1. For example, inFormulae 3 and 4, 0.1≤x≤1/3, 0<y≤0.5, 0<z≤0.01, 1/3≤(1-x-y-z)≤0.97, and0<α≤0.01. For example, in Formulae 3 and 4, 0.1≤x≤1/3, 0.05≤y≤0.3,0<z≤0.01, 1/3≤(1-x-y-z)≤0.97, and 0<α≤0.01. For example, in Formulae 3and 4, 0.1≤x≤1/3, 0.05≤y≤0.3, 0<z≤0.009, 1/3≤(1-x-y-z)≤0.95, and0<α≤0.0013. For example, in Formulae 3 and 4, 0.1<x≤1/3, 0.05≤y≤0.3,0<z≤0.009, 0.33≤(1-x-y-z)≤0.95, and 0<α≤0.0013.

The content of Ni in the nickel-based active material may be in a rangeof, for example, about 33 mol % to about 97 mol %, about 33 mol % toabout 95 mol %, for example, about 50 mol % to about 90 mol %, forexample, about 60 mol % to about 85 mol %, with respect to a totalamount of transition metals. The total amount of transition metalsrefers to a total amount of nickel, cobalt, and manganese in Formula 3and a total amount of nickel, cobalt, and aluminium in Formula 4.

The nickel-based active material is, for example,Li(Ni_(0.6)Co_(0.2)Mn_(0.2))_(1-a)M_(a)O_(2-α)X_(α),Li(Ni_(0.5)Co_(0.2)Mn_(0.3))_(1-a)M_(a)O_(2-α)X_(α),Li(Ni_(0.7)Co_(0.15)Mn_(0.15))_(1-a)M_(a)O_(2-α)X_(α),Li(Ni_(0.85)Co_(0.1)Al_(0.05))_(1-a)M_(a)O_(2-α)X_(α), orLi(Ni_(0.91)Co_(0.06)Mn_(0.03))_(1-a)M_(a)O_(2-α)X_(α), wherein 0<a<0.01and 0<α≤0.01, M is at least one element selected from B, Mg, Ca, Sr, Ba,Ti, V, W, Cr, Fe, Cu, Zr, and Al, and X is at least one selected fromPO₄, BO₂, B₄O₇, B₃O₅, and F. For example, 0<a<0.009 and 0<α≤0.0013.

The nickel-based active material may have a particle structure andcharacteristic substantially the same as or similar to those of theabove-described nickel-based active material precursor, except thatlithium is arranged in the crystal structure and the hydroxide ischanged to an oxide.

The nickel-based active material includes, for example, a particulatestructure including a core portion, an intermediate layer portion on thecore portion, and a shell portion on the intermediate layer portion, inwhich the intermediate layer portion and the shell portion includeprimary particles radially arranged on the core portion, and the coreportion, the intermediate layer portion, and the shell portion includedifferent cations and/or anions, wherein the cation is at least oneselected from B, Mg, Ca, Sr, Ba, Ti, V, Cr, Fe, Cu, Zr, and Al, and theanion is at least one selected from phosphate (PO₄), BO₂, B₄O₇, B₃O₅,and F.

The nickel-based active material includes, for example, secondaryparticles including a plurality of particulate structures, in which eachparticulate structure includes a core portion, an intermediate layerportion on the core portion, and a shell portion on the intermediatelayer portion, the porosity of the core portion, the intermediate layerportion, and the shell portion is sequentially reduced, the intermediatelayer portion and the shell portion include primary particles radiallyarranged on the core portion, and each of the core portion and theintermediate layer portion includes a cation or anion different fromthat of the shell portion, wherein the cation includes at least oneselected from B, Mg, Ca, Sr, Ba, Ti, V, Cr, Fe, Cu, Zr, and Al, and theanion includes at least one selected from phosphate (PO₄), BO₂, B₄O₇,B₃O₅, and F.

In the nickel-based active material, each of the core portion and theintermediate layer portion includes a cation or anion different fromthat of the shell portion. The cations are, for example, metal cationshaving a larger ionic radius than that of Ni cations. By including metalcations having a larger ionic radius, cation mixing is suppressed orreduced in the crystal lattice, and as a result, the elution of nickelions is suppressed or reduced, and thus the structural stability of aportion including the cations is enhanced. Anions are, for example,anions having a higher electronegativity than oxygen. By includinganions having such a great electronegativity, binding strength between atransition metal layer and an anion layer in the crystal lattice isenhanced, thereby enhancing the structural stability of a portionincluding the anions. For example, the instability of an anion layer dueto lithium entry during charging and discharging is reduced, and gasgeneration due to oxygen release is suppressed or reduced. Therefore,the nickel-based active material provides both a high discharge capacityand excellent structural stability.

The amount of cations included in the nickel-based active material is,for example, 0.9 mol % or less, 0.7 mol % or less, 0.5 mol % or less,0.3 mol % or less, or 0.28 mol % or less with respect to a total amountof the nickel-based active material. For example, the amount of thecations included in the nickel-based active material is in a range ofabout 0.0001 mol % to about 0.9 mol %, about 0.001 mol % to about 0.7mol %, about 0.001 mol % to about 0.5 mol %, about 0.001 mol % to about0.3 mol %, or about 0.001 mol % to about 0.28 mol % with respect to thetotal amount of the nickel-based active material. When the amount of thecations is too large, doping in the shell portion is difficult such thatthe amount of impurities increases, and the porosity of the shellportion is further increased. Therefore, a lithium battery includingsuch nickel-based active material (e.g., a nickel-based active materialin which the amount of cations is outside of the recited range) exhibitsreduced volume capacity and deteriorated cycle characteristics.

The amount of the anions included in the nickel-based active materialis, for example, 0.06 mol % or less, 0.05 mol % or less, 0.04 mol % orless, or 0.03 mol % or less, with respect to the total amount of thenickel-based active material. The amount of the anions included in thenickel-based active material is in a range of, for example, about 0.0001mol % to about 0.06 mol %, about 0.001 mol % to about 0.05 mol %, about0.005 mol % to about 0.04 mol %, or about 0.01 mol % to about 0.03 mol%, with respect to the total amount of the nickel-based active material.

The amount of the cation(s) included in the shell portion of thenickel-based active material is in a range of greater than about 0 mol %to about 2 mol %. For example, 2.0 mol % or less, 1.8 mol % or less, 1.6mol % or less, 1.4 mol % or less, 1.33 mol % or less, or 0.41 mol % orless, with respect to the total amount of the shell portion. Forexample, the amount of the cation(s) included in the shell portion ofthe nickel-based active material is in a range of about 0.0001 mol % toabout 2.0 mol %, about 0.001 mol % to about 1.8 mol %, about 0.001 mol %to about 1.6 mol %, about 0.001 mol % to about 1.4 mol %, about 0.001mol % to about 1.33 mol %, or about 0.001 mol % to about 0.41 mol % withrespect to the total amount of the shell portion.

A total amount of the anions included in the core portion and theintermediate layer portion of the nickel-based active material is, forexample, 1.0 mol % or less, 0.8 mol % or less, 0.6 mol % or less, 0.4mol % or less, or 0.18 mol % or less with respect to a total amount ofthe core portion and the intermediate layer portion. The total amount ofthe anions included in the core portion and the intermediate layerportion of the nickel-based active material is in a range of about0.0001 mol % to about 1.0 mol %, about 0.001 mol % to about 0.8 mol %,about 0.001 mol % to about 0.6 mol %, about 0.001 mol % to about 0.4 mol%, or about 0.001 mol % to 0.18 mol %, with respect to the total amountof the core portion and the intermediate layer portion.

When the whole nickel-based active material, the core portion of thenickel-based active material, the intermediate layer portion of thenickel-based active material, and/or the shell portion of thenickel-based active material include cations and/or anions within theabove-described amount ranges, the structural stability of thenickel-based active material is further enhanced.

A method of preparing a nickel-based active material from thenickel-based active material precursor is not particularly limited, andmay be, for example, a dry process.

The nickel-based active material may be prepared by, for example, mixinga lithium precursor and a nickel-based active material precursor in acertain (set) molar ratio and primarily heat-treating the resultingmixture at a temperature of about 600° C. to about 800° C.

The lithium precursor is, for example, lithium hydroxide, lithiumfluoride, lithium carbonate, or a mixture thereof. A mixing ratio of thelithium precursor to the nickel-based active material precursor isadjusted stoichiometrically, for example, to prepare the nickel-basedactive material of Formula 3 or Formula 4.

The mixing process may be dry mixing, and may be performed using a mixerand/or the like. The dry mixing process may be performed using a mill.Milling conditions are not particularly limited, but milling may becarried out such that that the precursor used as a starting materialundergoes little deformation such as pulverization and/or the like. Thesize of the lithium precursor mixed with the nickel-based activematerial precursor may be pre-controlled (pre-set). The size (meanparticle diameter) of the lithium precursor is in a range of about 5 μmto about 15 μm, for example, about 10 μm. By performing milling on thelithium precursor (having such size) and the nickel-based activematerial precursor at about 300 rpm to about 3,000 rpm, a desiredmixture may be obtained. In the milling process, when an internaltemperature of a mixer is increased by 30° C. or more, a cooling processmay be performed such that the internal temperature of the mixture ismaintained at room temperature (25° C.).

The primarily heat treatment is performed in an oxidative gasatmosphere. The oxidative gas atmosphere uses an oxidative gas such asoxygen or air, and the oxidative gas includes (e.g., consists of), forexample, about 10 vol % to about 20 vol % of oxygen or air and about 80vol % to about 90 vol % of inert gas. The primarily heat treatment maybe performed at a densification temperature or less as a reactionbetween the lithium precursor and the nickel-based active materialprecursor proceeds. The densification temperature is a temperature atwhich sufficient crystallization occurs to realize a charging capacitythat the active material is capable of providing. The primarily heattreatment is performed at a temperature of, for example, about 600° C.to about 800° C., for example, about 650° C. to about 800° C. Theprimarily heat treatment time varies depending on the heat treatmenttemperature, but is, for example, in a range of about 3 hours to about10 hours.

The method of preparing a nickel-based active material may furtherinclude, after the primarily heat treatment, a second heat treatmentprocess performed in an oxidative gas atmosphere while the vent isblocked. The second heat treatment is performed at a temperature of, forexample, about 700° C. to about 900° C. The second heat treatment timevaries depending on the second heat treatment temperature, but is in arange of, for example, about 3 hours to about 10 hours.

In the second heat treatment process of secondary particles of thenickel-based active material, a hetero-element compound containing atleast one selected from Zr, Ti, Al, Mg, W, P, and B may be furtheradded. The hetero-element compound is a compound containing at least oneselected from Zr, Ti, Al, Mg, W, P, and B. Non-limiting examples of thehetero-element compound include titanium oxide, zirconium oxide, andaluminium oxide. The hetero-element compound may include both lithium(Li) and a hetero-element. The hetero-element compound is, for example,i) an oxide of at least one selected from Zr, Ti, Al, Mg, W, P, and B;or ii) an oxide containing lithium and at least one selected from Zr,Ti, Al, Mg, W, P, and B. The hetero-element compound is, for example,ZrO₂, Al₂O₃, LiAlO₂, Li₂TiO₃, Li₂ZrO₃, LiBO₃, Li₃PO₄, and/or the like.The amount of the hetero-element compound is in a range of about 0.0005parts by weight to about 0.01 parts by weight with respect to 100 partsby weight of the nickel-based active material. The presence anddistribution of the oxide containing the hetero-element may be confirmedthrough electron probe micro-analysis (EPMA).

A lithium secondary battery according to one or more embodimentsincludes a positive electrode including the above-described nickel-basedactive material for a lithium secondary battery, a negative electrode,and an electrolyte arranged therebetween.

A method of manufacturing a lithium secondary battery is notparticularly limited, and any suitable method may be used. The lithiumsecondary battery may be manufactured by, for example, the followingmethod.

A positive electrode and a negative electrode are respectivelyfabricated by applying a composition for forming a positive activematerial layer and a composition for forming a negative active materiallayer on respective current collectors and drying the resultingstructures.

The composition for forming a positive active material layer is preparedby mixing a positive active material, a conductive agent, a binder, anda solvent, and for the positive active material, a positive activematerial according to one or more embodiments is used.

The binder is a component that aids in binding between an activematerial and a conductive agent and binding between an active materialand a current collector, and is added in an amount of about 1 part byweight to about 50 parts by weight with respect to 100 parts by weightof a total amount of the positive active material. Non-limiting examplesof the binder may include polyvinylidene fluoride, polyvinyl alcohol,carboxymethylcellulose (CMC), starch, hydroxypropylcellulose,regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene,polyethylene, polypropylene, ethylene-propylene-diene terpolymer (EPDM),sulfonated EPDM, styrene-butadiene rubber, fluorine rubber, and variouscopolymers.

The conductive agent is not particularly limited as long as it does notcause any chemical change in the fabricated battery and hasconductivity, and non-limiting examples thereof include graphite (suchas natural graphite and/or artificial graphite); carbonaceous materials(such as carbon black, acetylene black, ketjen black, channel black,furnace black, lamp black, and/or thermal black); conductive fibers(such as carbon fibers and/or metallic fibers); metal powder (such ascarbon fluoride powder, aluminium powder, and/or nickel powder);conductive whiskers (such as zinc oxide and/or potassium titanate);conductive metal oxides (such as titanium oxide); and conductivematerials (such as polyphenylene derivatives).

As a non-limiting example of the solvent, N-methylpyrrolidone and/or thelike may be used.

The amounts of the binder, the conductive agent, and the solvent are atgeneral levels (e.g., at any suitable level).

A positive electrode current collector has a thickness of about 3 μm toabout 500 μm, and is not particularly limited as long as it has highconductivity without causing chemical changes in the fabricated battery.Examples of the positive electrode current collector include stainlesssteel, aluminium, nickel, titanium, sintered carbon, and aluminium orstainless steel that is surface-treated with carbon, nickel, titaniumand/or silver, without limitation. The current collector may beprocessed to have fine irregularities on the surfaces thereof so as toenhance adhesive strength of the current collector to the positiveactive material, and may be used in any of various suitable formsincluding films, sheets, foils, nets, porous structures, foams, and/ornon-woven fabrics.

Separately, the composition for forming a negative active material layeris prepared by mixing a negative active material, a binder, a conductiveagent, and a solvent. As the negative active material, a materialcapable of intercalating and deintercalating lithium ions is used. As anon-limiting example of the negative active material, a carbonaceousmaterial such as graphite, Li metal or an alloy thereof, and/or asilicon oxide-based material may be used.

The binder is added in an amount of about 1 part by weight to about 50parts by weight with respect to 100 parts by weight of a total weight ofthe negative active material. In a non-limiting example, the binder maybe the same binder as that of the positive electrode.

The conductive agent is used in an amount of about 1 part by weight toabout 5 parts by weight with respect to 100 parts by weight of the totalweight of the negative active material. When the amount of theconductive agent is within the above-described range, the finallyobtained electrode has excellent (or suitable) conductivity.

The amount of the solvent is in a range of about 1 part by weight toabout 10 parts by weight with respect to 100 parts by weight of thetotal weight of the negative active material. When the amount of thesolvent is within the above range, an operation for forming a negativeactive material layer is facilitated.

As the conductive agent and the solvent for the negative electrode, thesame conductive agent and solvent as those used in fabricating thepositive electrode may be used.

A negative electrode current collector may be fabricated to a thicknessof about 3 μm to about 500 μm. The negative electrode current collectoris not particularly limited as long as it has conductivity withoutcausing chemical changes in the fabricated battery, and examples of thenegative electrode current collector include copper, stainless steel,aluminium, nickel, titanium, sintered carbon, copper and/or stainlesssteel that is surface-treated with carbon, nickel, titanium and/orsilver, and aluminium-cadmium alloys, without limitation. In addition,as in the positive electrode current collector, the negative electrodecurrent collector may be processed to have fine irregularities on thesurfaces thereof so as to enhance adhesive strength of the currentcollector to the negative active material, and may be used in any ofvarious suitable forms including films, sheets, foils, nets, porousstructures, foams, and/or non-woven fabrics.

A separator is disposed between the positive and negative electrodesfabricated by the above-described processes.

The separator has a pore diameter of about 0.01 μm to about 10 μm and athickness of about 5 μm to about 300 μm. For example, the separator maybe an olefin-based polymer (such as polypropylene, polyethylene, and/orthe like); a sheet or non-woven fabric made of glass fiber; and/or thelike. When a solid electrolyte (such as a polymer and/or the like) isused as an electrolyte, the solid electrolyte may also act as aseparator.

A lithium salt-containing non-aqueous electrolyte includes (e.g.,consists of) a non-aqueous electrolyte and a lithium salt. As thenon-aqueous electrolyte, a non-aqueous electrolytic solution, an organicsolid electrolyte, and/or an inorganic solid electrolyte may be used.

As the non-aqueous electrolytic solution, any of aprotic organicsolvents, for example, N-methyl-2-pyrrolidone, propylene carbonate,ethylene carbonate, butylene carbonate, dimethyl carbonate, diethylcarbonate, γ-butyrolactone, 1,2-dimethoxy ethane, 2-methyltetrahydrofuran, dimethylsulfoxide, 1,3-dioxolane, N,N-formamide,N,N-dimethylformamide, dioxolane, acetonitrile, nitromethane, methylformate, methyl acetate, phosphoric acid triester, trimethoxy methane,dioxolane derivatives, sulfolane, methyl sulfolane,1,3-dimethyl-2-imidazolidinone, propylene carbonate derivatives,tetrahydrofuran derivatives, ether, methyl propionate, and ethylpropionate may be used, but the present disclosure is not limitedthereto.

Non-limiting examples of the organic solid electrolyte includepolyethylene derivatives, polyethylene oxide derivatives, polypropyleneoxide derivatives, phosphoric acid ester polymers, polyester sulfide,polyvinyl alcohols, and polyvinylidene fluoride. Non-limiting examplesof the inorganic solid electrolyte include Li₃N, LiI, Li₅NI₂,Li₃N—LiI—LiOH, Li₂SiS₃, Li₄SiO₄, Li₄SiO₄—LiI—LiOH, and Li₃PO₄—Li₂S—SiS₂.

The lithium salt is a material that is readily soluble in thenon-aqueous electrolyte, and non-limiting examples of the lithium saltinclude LiCl, LiBr, LiI, LiClO₄, LiBF₄, LiB₁₀Cl₁₀, LiPF₆, LiCF₃SO₃,LiCF₃CO₂, LiAsF₆, LiSbF₆, LiAlCl₄, CH₃SO₃Li, (CF₃SO₂)₂NLi, (FSO₂)₂NLi,lithium chloroborate, lower aliphatic carboxylic acid lithium, lithiumtetraphenyl borate, and lithium imide.

FIG. 4 is a schematic cross-sectional view illustrating a structure of alithium secondary battery 1 according to an embodiment. Referring toFIG. 4 , the lithium secondary battery 1 includes a positive electrode3, a negative electrode 2, and a separator 4. The positive electrode 3,the negative electrode 2, and the separator 4 are wound or folded, andthen accommodated in a battery case 5. Subsequently, an organicelectrolytic solution is injected into the battery case 5 and thebattery case 5 is sealed by a cap assembly 6, thereby completing themanufacture of the lithium secondary battery 1. The battery case 5 mayhave a cylindrical shape, a rectangular shape or a thin-film shape. Forexample, the lithium secondary battery 1 may be a large-sized thin filmbattery. The lithium secondary battery 1 may be a lithium ion battery.

A separator may be disposed between a positive electrode and a negativeelectrode to thereby form a battery assembly. The battery assembly maybe stacked in a bi-cell structure, and impregnated with an organicelectrolytic solution, and the resulting structure may be accommodatedin a pouch and hermetically sealed, thereby completing the manufactureof a lithium ion polymer battery. In one or more embodiments, aplurality of battery assemblies are stacked to form a battery pack, andthe battery pack may be used in any device requiring high capacityand/or high-power output. For example, the battery pack may be used innotebook computers, smartphones, electric vehicles, and/or the like. Inaddition, the lithium secondary battery may be used in electric vehicles(EVs) due to excellent storage stability at high temperatures, excellentlifespan characteristics, and excellent rate capability thereof. Forexample, the lithium secondary battery may be used in hybrid vehiclessuch as plug-in hybrid electric vehicles (PHEVs).

Hereinafter, the present disclosure will be described in further detailwith reference to the following examples and comparative examples.However, these examples are provided for illustrative purposes only andare not intended to limit the scope of the present disclosure.

Preparation Example 1: Preparation of Nickel-Based Active MaterialPrecursor (Core/Intermediate/Shell=P/P/W)

A nickel-based active material precursor was synthesized throughco-precipitation. In the following preparation process, nickel sulfate(NiSO₄.6H₂O), cobalt sulfate (CoSO₄.7H₂O), and manganese sulfate(MnSO₄.H₂O), as metal raw materials for forming a nickel-based activematerial precursor, were dissolved in distilled water as a solvent in amolar ratio of Ni:Co:Mn of 70:15:15 to prepare a mixed solution. Inaddition, ammonia water (NH₄OH) (as a complexing agent for forming acomplex compound), an aqueous disodium phosphate (Na₂HPO₄) solution (asa phosphate-containing compound), tungsten oxide (WO₂) dissolved in anaqueous sodium hydroxide solution (as a tungsten-containing compound),and sodium hydroxide (NaOH) (as a precipitating agent and a pH adjuster)were prepared.

First Process: 3.0 kW/m³, NH₃.H₂O 0.50 M, pH of 11.0 to 11.5, ReactionTime of 6 Hours

Ammonia water was added at a concentration of 0.50 M into a reactorequipped with a stirrer. While a stirring power of 3.0 kW/m³ and areaction temperature of 50° C. were maintained, 2 mol/L (M) of metal rawmaterials (a mixed solution of nickel sulfate, cobalt sulfate, andmanganese sulfate), 0.50 M of ammonia water, and an aqueous disodiumphosphate solution were added at flow rates of 4.3 ml/min, 0.7 ml/min,and 1.6 ml/min, respectively, to allow a reaction to occur therebetween.

Subsequently, NaOH was added thereto to maintain the pH of the reactionmixture. The pH of the reaction mixture in the reactor was maintained at11.00 to 11.50. The reaction mixture was stirred for 6 hours within sucha pH range to allow a first process reaction to occur. As a result ofthe reaction, it was confirmed that the obtained core particles had anaverage size of about 8 μm to about 9 μm. A concentration of the aqueousdisodium phosphate solution used in the preparation of the core wasdetermined to give half of required content of phosphate in resultingprecursor.

Second Process: 2.5 kW/m³, NH₃.H₂O 0.55 M, pH: 10.5 to 11, ReactionTime: 13 Hours

After the first process reaction, the internal stirring power of thereactor was reduced to 2.5 kW/m³ and while the reaction temperature wasmaintained at 50° C., 2 mol/L (M) of metal raw materials, 0.55 M ofammonia water, and an aqueous disodium phosphate solution were addedinto the reactor at flow rates of 5.38 ml/min, 0.9 ml/min, and 2.0ml/min, respectively. At this time, the concentration of the complexingagent was maintained at 0.55 M. NaOH was added to the reaction mixtureto maintain the pH thereof. The pH of the reaction mixture in thereactor was maintained at 10.50 to 11.00. The reaction mixture wasstirred for 13 hours within the above pH range to allow a second processreaction to occur. As a result, it was confirmed that product particlesincluding a core and an intermediate layer, which were obtained throughthe reaction, had an average size of 11 μm to 12 μm. A concentration ofthe aqueous disodium phosphate solution used in the preparation of theintermediate layer was determined to give half of required content ofphosphate in resulting precursor.

Third Process: 2.0 kW/m³, NH₃.H₂O 0.60 M, pH: 10.5 to 11, Reaction Time:12 Hours

After the second process reaction, half of the volume of the reactionproduct was removed from the reactor and the amount of the reactionproduct in the reactor was diluted to 50 vol %. The internal stirringpower of the reactor was reduced to 2.0 kW/m³ and while the reactiontemperature was maintained at 50° C., 2 mol/L (M) of metal rawmaterials, 0.60 M of ammonia water, and an aqueous tungsten oxide (WO₂)solution were added into the reactor at flow rates of 4.3 ml/min, 0.8ml/min, and 1.6 ml/min, respectively. At this time, the concentration ofthe complexing agent was maintained at 0.60 M. NaOH was added to thereaction mixture to maintain the pH thereof. The pH of the reactionmixture in the reactor was maintained at 10.50 to 11.00. The reactionmixture was stirred for 12 hours within the above pH range to allow athird process reaction to occur. As a result, it was confirmed that themean particle diameter (D50) of the product particles reached a targetvalue, i.e., 13 μm to 14 μm. An amount of the tungsten oxide (WO₂) addedin the preparation of the shell was determined to give required contentof tungsten in the resulting nickel-based active material precursor.

Post-Processing

The reaction product was washed to remove unnecessary ions from theproduct particles, and then the washed resulting product was dried byhot air at about 150° C. for 24 hours, thereby obtaining a nickel-basedactive material precursor.

In the nickel-based active material precursor, with respect to a totalamount of the nickel-based active material precursor, the content ofphosphate was 0.06 mol %, and the content of tungsten was 0.28 mol %. Inthe shell portion of the nickel-based active material precursor, thecontent of phosphate was 0 mol %, and the content of tungsten was 0.41mol %, and with respect to a total amount of core and intermediate layerportions of the nickel-based active material precursor, the content ofphosphate was 0.18 mol %, and the content of tungsten was 0 mol %.

Preparation Example 2: Preparation of Nickel-Based Active MaterialPrecursor (Core/Intermediate/Shell=P/P/W)

A nickel-based active material precursor was prepared in the same (orsubstantially the same) manner as in Preparation Example 1, except thatthe amount of tungsten added in preparation of a shell was changed to3.7 mol % with respect to a total amount of the nickel-based activematerial precursor.

As a result of analyzing the synthesized precursor, the content ofphosphate was 0.06 mol %, and the content of tungsten (W) was 0.9 mol %.Thus, it was confirmed that even though an excess amount of tungsten wasadded, the content of tungsten included in the shell was 0.9 mol % withrespect to the total amount of the nickel-based active materialprecursor. In the shell portion of the nickel-based active materialprecursor, the content of phosphate was 0 mol %, and the content oftungsten was 1.33 mol %, and with respect to a total amount of core andintermediate layer portions of the nickel-based active materialprecursor, the content of phosphate was 0.18 mol %, and the content oftungsten was 0 mol %.

Comparative Preparation Example 1: Preparation of Nickel-Based ActiveMaterial Precursor (Core/Intermediate/Shell=0/0/0)

A nickel-based active material precursor was synthesized using the sameraw materials as those used in Preparation Example 1 throughco-precipitation, which will be described below.

First Process: 3.0 kW/m³, NH₃ 0.35 M, pH: 11.0 to 11.5, Reaction Time: 6Hours

A first process reaction was performed in the same (or substantially thesame) manner as in Preparation Example 1, except that the concentrationof the complexing agent (ammonia water) was changed to 0.35 M instead of0.50 M, and the phosphate-containing compound was not added.

Second Process: 2.5 kW/m³, NH₃ 0.40 M, pH: 10.5 to 11.0, Reaction Time:21 Hours

A second process reaction was performed in the same (or substantiallythe same) manner as in Preparation Example 1, except that theconcentration of the complexing agent (ammonia water) was changed to0.40 M instead of 0.55 M, the phosphate-containing compound was notadded, and the reaction time was changed to 21 hours instead of 13hours.

Third Process: 2.0 kW/m³, NH₃ 0.40 M, pH: 10.5 to 11.0, Reaction Time:23 Hours

After the second process reaction, half of the volume of the reactionproduct was removed from the reactor and the amount of the reactionproduct in the reactor was diluted to 50 vol %. The internal stirringpower of the reactor was reduced to 2.0 kW/m³ and while the reactiontemperature was maintained at 50° C., metal raw materials and ammoniawater were added into the reactor at flow rates of 7.2 ml/min and 0.8ml/min, respectively. At this time, the concentration of the complexingagent (ammonia water) was maintained at 0.40 M. NaOH was added to thereaction mixture to maintain the pH thereof. The pH of the reactionmixture in the reactor was maintained at 10.50 to 11.00. The reactionmixture was stirred for 23 hours within the above pH range to allow athird process reaction to occur. As a result, it was confirmed that theD50 of the product particles reached a target value, i.e., 13 μm to 14μm.

Post-Processing

Post-processing was carried out in the same (or substantially the same)manner as in Preparation Example 1.

As a result of analyzing the synthesized precursor, the content ofphosphate was 0 mol %, and the content of tungsten (W) was 0 mol %.

Comparative Preparation Example 2: Preparation of Nickel-Based ActiveMaterial Precursor (Core/Intermediate/Shell=W/W/W)

A nickel-based active material precursor was synthesized using the sameraw materials as those used in Preparation Example 1 throughco-precipitation, which will be described below.

First Process: 3.0 kW/m³, NH₃ 0.35 M, pH: 11.0 to 11.5, Reaction Time: 6Hours

A first process reaction was performed in the same (or substantially thesame) manner as in Preparation Example 1, except that the concentrationof the complexing agent (ammonia water) was changed to 0.35 M instead of0.50 M, and an aqueous tungsten oxide solution was added at a flow rateof 0.5 ml/min instead of the phosphate-containing compound. An amount ofthe tungsten oxide (WO₂) added in the preparation of the core wasdetermined to give required content of tungsten in the resultingnickel-based active material precursor.

Second Process: 2.5 kW/m³, NH₃ 0.40 M, pH: 10.5 to 11.0, Reaction Time:21 Hours

A second process reaction was performed in the same (or substantiallythe same) manner as in Preparation Example 1, except that theconcentration of the complexing agent (ammonia water) was changed to0.40 M instead of 0.55 M, an aqueous tungsten oxide solution was addedat a flow rate of 0.7 ml/min instead of the phosphate-containingcompound, and the reaction time was changed to 21 hours instead of 13hours. An amount of the tungsten oxide (WO₂) added in the preparation ofthe intermediate layer was determined to give required content oftungsten in resulting nickel-based active material precursor.

Third Process: 2.0 kW/m³, NH₃ 0.40 M, pH: 10.5 to 11.0, Reaction Time:23 Hours

After the second process reaction, half of the volume of the reactionproduct was removed from the reactor and the amount of the reactionproduct in the reactor was diluted to 50 vol %. The internal stirringpower of the reactor was reduced to 2.0 kW/m³ and while the reactiontemperature was maintained at 50° C., metal raw materials, ammoniawater, and an aqueous tungsten oxide solution were added into thereactor at flow rates of 7.2 ml/min, 0.8 ml/min, and 0.9 ml/min,respectively. At this time, the concentration of the complexing agent(ammonia water) was maintained at 0.40 M. NaOH was added to the reactionmixture to maintain the pH thereof. The pH of the reaction mixture inthe reactor was maintained at 10.50 to 11.00. The reaction mixture wasstirred for 23 hours within the above pH range to allow a third processreaction to occur. As a result, it was confirmed that the D50 of theproduct particles reached a target value, i.e., 13 μm to 14 μm. Anamount of the tungsten oxide (WO₂) added in the preparation of the shellwas determined to give required content of tungsten in resultingnickel-based active material precursor.

Post-Processing

Post-processing was carried out in the same (or substantially the same)manner as in Preparation Example 1.

As a result of analyzing the synthesized precursor, the content ofphosphate was 0 mol %, and the content of tungsten (W) was 0.1 mol %.

Comparative Preparation Example 3: Preparation of Nickel-Based ActiveMaterial Precursor (Core/Intermediate/Shell=P/P/P)

A nickel-based active material precursor was synthesized using the sameraw materials as those used in Preparation Example 1 throughco-precipitation, which will be described below.

First Process: 3.0 kW/m³, NH₃ 0.35 M, pH: 11.0 to 11.5, Reaction Time: 6Hours

A first process reaction was performed in the same (or substantially thesame) manner as in Preparation Example 1, except that the concentrationof the complexing agent (ammonia water) was changed to 0.35 M instead of0.50 M, and an aqueous disodium phosphate solution was added at a flowrate of 0.7 ml/min instead of a flow rate of 1.6 ml/min. A concentrationof the aqueous disodium phosphate solution used in the preparation ofthe core was determined to give required content of phosphate inresulting precursor.

Second Process: 2.5 kW/m³, NH₃ 0.40 M, pH: 10.5 to 11.0, Reaction Time:21 Hours

A second process reaction was performed in the same (or substantiallythe same) manner as in Preparation Example 1, except that theconcentration of the complexing agent (ammonia water) was changed to0.40 M instead of 0.55 M, an aqueous disodium phosphate solution wasadded at a flow rate of 0.9 ml/min instead of 2.0 ml/min, and thereaction time was changed to 21 hours instead of 13 hours. Aconcentration of the aqueous disodium phosphate solution used in thepreparation of the intermediate layer was determined to give requiredcontent of phosphate in resulting precursor.

Third Process: 2.0 kW/m³, NH₃ 0.40 M, pH: 10.5 to 11.0, Reaction Time:23 Hours

After the second process reaction, half of the volume of the reactionproduct was removed from the reactor and the amount of the reactionproduct in the reactor was diluted to 50 vol %. The internal stirringpower of the reactor was reduced to 2.0 kW/m³ and while the reactiontemperature was maintained at 50° C., metal raw materials, ammoniawater, and an aqueous disodium phosphate solution were added into thereactor at flow rates of 7.2 ml/min, 0.8 ml/min, and 1.2 ml/min,respectively. At this time, the concentration of the complexing agent(ammonia water) was maintained at 0.40 M. NaOH was added to the reactionmixture to maintain the pH thereof. The pH of the reaction mixture inthe reactor was maintained at 10.50 to 11.00. The reaction mixture wasstirred for 23 hours within the above pH range to allow a third processreaction to occur. As a result, it was confirmed that the D50 of theproduct particles reached a target value, i.e., 13 μm to 14 μm. Aconcentration of the aqueous disodium phosphate solution used in thepreparation of the shell was determined to give required content ofphosphate in resulting precursor.

Post-Processing

Post-processing was carried out in the same (or substantially the same)manner as in Preparation Example 1.

As a result of analyzing the synthesized precursor, the content ofphosphate was 0.13 mol %, and the content of tungsten (W) was 0 mol %.

Example 1: Preparation of Nickel-Based Active Material

A composite metal hydroxide, which is the nickel-based active materialprecursor prepared according to Preparation Example 1, and lithiumhydroxide (LiOH) were mixed in a molar ratio of 1:1 and subjected tofirst heat treatment in an oxygen atmosphere at about 780° C. for 6hours, thereby obtaining nickel-based active material secondaryparticles (nickel-based active material intermediate). The obtainedsecondary particles were pulverized and then subjected to second heattreatment in an oxygen atmosphere at about 740° C. for 6 hours, therebyobtaining nickel-based active material secondary particles each having atriple structure including a core, intermediate layer and a shell.

With respect to a total amount of the nickel-based active material, thecontent of phosphate was 0.06 mol %, and the content of tungsten was0.28 mol %.

In a shell portion of the nickel-based active material, the content ofphosphate was 0 mol %, and the content of tungsten was 0.41 mol %, andwith respect to a total amount of core and intermediate layer portionsof the nickel-based active material, the content of phosphate was 0.18mol %, and the content of tungsten was 0 mol %.

Example 2: Preparation of Nickel-Based Active Material

A nickel-based active material was prepared in the same (orsubstantially the same) manner as in Example 1, except that thenickel-based active material precursor prepared according to PreparationExample 2 was used instead of the nickel-based active material precursorof Preparation Example 1.

In the nickel-based active material, the content of phosphate was 0.06mol %, and the content of tungsten was 0.9 mol %.

In a shell portion of the nickel-based active material, the content ofphosphate was 0 mol %, and the content of tungsten was 1.33 mol %, andwith respect to a total amount of core and intermediate layer portionsof the nickel-based active material, the content of phosphate was 0.18mol %, and the content of tungsten was 0 mol %.

Comparative Example 1: Preparation of Nickel-Based Active Material

Nickel-based active material secondary particles were obtained in thesame (or substantially the same) manner as in Example 1, except that thenickel-based active material precursor prepared according to ComparativePreparation Example 1 was used instead of the nickel-based activematerial precursor of Preparation Example 1.

As a result of analyzing the nickel-based active material, the contentof phosphate was 0 mol %, and the content of tungsten (W) was 0 mol %.

Comparative Example 2: Preparation of Nickel-Based Active Material

Nickel-based active material secondary particles were obtained in thesame (or substantially the same) manner as in Example 1, except that thenickel-based active material precursor prepared according to ComparativePreparation Example 2 was used instead of the nickel-based activematerial precursor of Preparation Example 1.

As a result of analyzing the nickel-based active material, the contentof phosphate was 0 mol %, and the content of tungsten (W) was 0.1 mol %.

Comparative Example 3: Preparation of Nickel-Based Active Material

Nickel-based active material secondary particles were obtained in thesame (or substantially the same) manner as in Example 1, except that thenickel-based active material precursor prepared according to ComparativePreparation Example 3 was used instead of the nickel-based activematerial precursor of Preparation Example 1.

As a result of analyzing the nickel-based active material, the contentof phosphate was 0.13 mol %, and the content of tungsten (W) was 0 mol%.

Manufacture Example 1: Coin Half-Cell

A coin half-cell was manufactured using the nickel-based active materialsecondary particles prepared according to Example 1 as a positive activematerial by the following method.

A mixture of 96 g of the nickel-based active material secondaryparticles of Example 1, 2 g of polyvinylidene fluoride, 47 g ofN-methylpyrrolidone as a solvent, and 2 g of carbon black as aconductive agent was uniformly dispersed using a mixer to remove airbubble from the mixture, thereby preparing a slurry for forming apositive active material layer.

The slurry prepared according to the above-described process was coatedonto aluminium foil using a doctor blade to fabricate a thin electrodeplate, and then dried at 135° C. for 3 hours or more, followed byroll-pressing and vacuum drying, thereby completing the fabrication of apositive electrode.

The positive electrode and Li metal as a counter electrode were used tomanufacture a 2032-type coin half-cell. A separator (thickness: about 16μm) formed of a porous polyethylene (PE) film was disposed between thepositive electrode and the Li metal counter electrode, and anelectrolytic solution was injected therebetween, thereby completing themanufacture of a 2032-type coin half-cell. As the electrolytic solution,a solution prepared by dissolving 1.1 M LiPF₆ in a mixed solvent ofethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volumeratio of 3:5 was used.

Comparative Manufacture Example 1: Manufacture of Coin Half-Cell

A lithium secondary battery was manufactured in the same (orsubstantially the same) manner as in Manufacture Example 1, except thatthe nickel-based active material prepared according to ComparativeExample 1 was used instead of the nickel-based active material ofExample 1.

Comparative Manufacture Example 2: Manufacture of Coin Half-Cell

A lithium secondary battery was manufactured in the same (orsubstantially the same) manner as in Manufacture Example 1, except thatthe nickel-based active material prepared according to ComparativeExample 2 was used instead of the nickel-based active material ofExample 1.

Comparative Manufacture Example 3: Manufacture of Coin Half-Cell

A lithium secondary battery was manufactured in the same (orsubstantially the same) manner as in Manufacture Example 1, except thatthe nickel-based active material prepared according to ComparativeExample 3 was used instead of the nickel-based active material ofExample 1.

Evaluation Example 1: Particle Size Analysis (Active MaterialsPrecursor)

Particle size analysis was performed on the nickel-based active materialprecursors prepared according to Preparation Example 1 and ComparativePreparation Examples 1 to 3. The particle size analysis results thereofare shown in Table 1 below. In Table 1, D10, D50, and D90 denoteparticle diameters corresponding to 10%, 50%, and 90%, respectively,when the particle diameters of the respective particles are measured andthe volumes thereof are cumulated starting from the smallest particles.That is, it can be confirmed that the prepared active materialprecursors have a similar particle diameter distribution.

TABLE 1 Classification D10 D50 D90 Preparation 10.1 13.4 17.1 Example 1Comparative 10.4 12.9 15.7 Preparation Example 1 Comparative 9.7 13.217.1 Preparation Example 2 Comparative 9.6 12.9 16.6 Preparation Example3

Evaluation Example 2: Analysis of Composition (Active MaterialsPrecursor)

The composition of each of the nickel-based active material precursorsprepared according to Preparation Examples 1 and 2 and ComparativePreparation Examples 1 to 3 is shown in Table 2 below. The compositionwas analyzed using ICP.

TABLE 2 Total amount of core Total amount of portion and Shellnickel-based active intermediate layer portion material precursorportion (mol %) (mol %) (mol %) [mol %] W PO₄ W PO₄ W PO₄ Comparative —— — — — — Preparation Example 1 Comparative 0.1 — 0.1  — 0.1  —Preparation Example 2 Comparative — 0.13 — 0.13 — 0.13 PreparationExample 3 Preparation — 0.18 0.41 — 0.28 0.06 Example 1 Preparation —0.18 1.33 — 0.90 0.06 Example 2

Referring to Table 2, the composition of a cation and an anion doped inthe nickel-based active material precursor of Preparation Examples 1 and2 were confirmed.

It was confirmed that both the cation and the anion were doped in thenickel-based active material precursor of Preparation Examples 1 and 2,there was no doping in the case of Comparative Preparation Example 1,the cation was doped in the case of Comparative Preparation Example 2,and the anion was doped in the case of Comparative Preparation Example3. The total amount of the core portion and the intermediate layerportion is the amount of cations/anions with respect to a total volumeof these regions, the amount of the shell portion is the amount ofcations/anions with respect to a volume of the shell portion, and thetotal amount of the nickel-based active material precursor is the amountof cations/anions with respect to a total volume of the nickel-basedactive material precursor.

Evaluation Example 3: Residual Lithium Analysis (Active Material)

Residual lithium of each of the nickel-based active material of Example1 and Comparative Examples 1 to 3 was analyzed using the followingmethod.

10 g of each sample was mixed with 100 ml of distilled water, and theresulting mixture was stirred at 300 rpm for 30 minutes. 50 ml of aliquid filtered from the mixed solution was collected and mixed with 100ml of pure water, and was then titrated with a hydrochloric acidsolution.

The amounts of lithium carbonate and lithium hydroxide were calculatedfrom equivalence point 1 (EP1) and equivalence point 2 (EP2) inaccordance with the injection of hydrochloric acid, and total residuallithium was calculated from EP2.

TABLE 3 Li₂CO₃ LiOH Total residual [wt %] [wt %] lithium [ppm] Example 10.120 0.605 1981 Comparative 0.206 0.643 2252 Example 1 Comparative0.164 0.498 1753 Example 2 Comparative 0.259 0.871 3013 Example 3

From the results of Table 3, it was confirmed that the amount ofresidual lithium was rapidly increased in Comparative Example 3 wherephosphate was included in a shell, compared to the case of ComparativeExample 1 not including an additive. In contrast, the amount of residuallithium was reduced in the cases of Example 1 and Comparative Example 2where tungsten was included in a shell, and the case of ComparativeExample 2 exhibiting a high concentration of tungsten had the smallestamount of residual lithium. From these results, it was confirmed thatwhen tungsten was present in a shell layer, the amount of residuallithium was reduced.

When the amount of residual lithium is increased to 3,000 ppm or more,gas generation is rapidly increased during operation of a battery.

Evaluation Example 4: Structural Analysis of Active Material Particles

Scanning electron microscope (SEM) images of cross-sections of thenickel-based active materials prepared according to Examples 1 and 2were captured, and the results thereof are respectively shown in FIGS.2A and 2B.

Referring to FIG. 2A, the nickel-based active material of Example 1includes a porous core illustrated on the left lower side of thedrawing, an oriented intermediate layer on the porous core, and anoriented shell on the intermediate layer.

Referring to FIG. 2B, it was confirmed that the nickel-based activematerial of Example 2 included an oriented intermediate layerillustrated on the left lower side of the drawing and an oriented shellon the oriented intermediate layer, and the porosity of the shellportion was increased, such that the shell portion had reduced density.

As illustrated in FIG. 2A, the intermediate layer and the shell arrangedon the porous core of the nickel-based active material of Example 1 hada radially arranged structure and had a lower porosity than that of thecore.

As illustrated in FIG. 2B, in the nickel-based active material ofExample 2, the shell had a higher porosity than that of the intermediatelayer. In one or more embodiments, the porous core also had a higherporosity than that of the intermediate layer. Thus, it was confirmedthat, when the content of tungsten was increased, the porosity of theactive material was increased.

As illustrated in FIGS. 2C and 2D, it was confirmed that a surface ofthe nickel-based active material of Example 2 included open poresconnecting the inside of active material particles to the surfacethereof.

Active material precursor particles respectively corresponding to theactive material particles of FIGS. 2A and 2B also had a structuresimilar to that of the active material particles.

A high-angle annular dark-field scanning transmission electronmicroscope (HAADF-STEM) image and an energy-dispersive X-rayspectroscopy (EDS) image of cross-sections of the nickel-based activematerials of Example 2 and Comparative Example 2 were captured, and theresults thereof are illustrated in FIGS. 3A and 3B.

As illustrated in FIG. 3A, it was confirmed that the concentration oftungsten (W) in a shell of the nickel-based active material of Example 2appeared darker, and as illustrated in FIG. 3B, it was confirmed thatthe concentration of tungsten (W) appeared uniformly throughoutparticles of the nickel-based active material of Comparative Example 2.

Thus, it was confirmed that, while tungsten (W) was doped in the shellof the nickel-based active material of Example 2, tungsten (W) was dopedthroughout particles of the nickel-based active material of ComparativeExample 2. From these results, it was confirmed that cations/anionsdoped in preparation of an active material precursor maintained aninitial concentration distribution in a structure of the precursor and astructure of an active material prepared therefrom without beingdiffused and/or mixed in active material particles.

Evaluation Example 5: Lifespan Characteristics at High-Temperature (45°C.)

High-temperature lifespan characteristics of the coin half-cellsmanufactured according to Manufacture Example 1 and ComparativeManufacture Examples 1 to 3 were evaluated using the following method.

Each of the coin half-cells of Manufacture Example 1 and ComparativeManufacture Examples 1 and 3 was charged/discharged once at 0.1 C and atroom temperature, thereby performing a formation operation, and then onecycle of charging and discharging at 0.2 C was performed on each coinhalf-cell to confirm initial charge/discharge characteristics thereof,and cycle characteristics of each coin half-cell were evaluated whilethe cycle of charging/discharging was repeated 50 times at 1 C and 45°C. The charging process was set such that it started with a constantcurrent (CC) and then was changed to a constant voltage (CV), and wascut off at 4.3 V and 0.05 C, and the discharging process was set suchthat it was cut off at 3.0 V in a CC mode. Changes in discharge capacityin accordance with cycle repetition were examined, high-temperaturelifespan was calculated by Equation 1 below, and some of the resultsthereof are shown in Table 4 below.

Lifespan (%)=(discharge capacity after 50^(th) cycle/discharge capacityafter 1^(st) cycle)×100  Equation 1

TABLE 4 High-temperature Classification lifespan (%) Manufacture Example1 98.4 Comparative 97.6 Manufacture Example 1 Comparative 98.0Manufacture Example 3

Referring to Table 4, it was confirmed that the coin half-cell ofManufacture Example 1 exhibited enhanced high-temperature lifespancharacteristics as compared to those of Comparative Manufacture Examples1 and 3.

Evaluation Example 6: Charge and Discharge Characteristics (InitialEfficiency and Capacity)

Each of the coin half-cells of Manufacture Example 1 and ComparativeManufacture Examples 1 to 3 was first charged/discharged once at 0.1 C,thereby performing a formation operation. Subsequently, initialcharge/discharge characteristics of each coin half-cell were examined byperforming one cycle of charging and discharging (1^(st) cycle) at 0.2 Cto confirm initial discharge capacity. The charging process was set suchthat it started with a constant current (CC) and then was changed to aconstant voltage (CV), and was cut off at 4.3 V and 0.05 C, and thedischarging process was set such that it was cut off at 3.0 V in a CCmode.

Initial charge efficiency (I.C.E) was measured according to Equation 2below.

Initial charge efficiency [%]=[discharge capacity at 1^(st) cycle/chargecapacity at 1^(st) cycle]×100  Equation 2

Initial charge efficiency and initial discharge capacity of each of thecoin half-cells of Manufacture Example 1 and Comparative ManufactureExamples 1 to 3 were measured, and the results thereof are shown inTable 5 below. Initial discharge capacity is discharge capacity wheninitial charge efficiency is measured.

TABLE 5 Initial charge Initial discharge efficiency [%] capacity [mAh/g]Manufacture Example 1 96.2 195.8 Comparative 94.1 194.4 ManufactureExample 1 Comparative 95.6 183.7 Manufacture Example 2 Comparative 95.0194.7 Manufacture Example 3

Referring to Table 5, it was confirmed that the coin half-cell ofManufacture Example 1 exhibited enhanced initial charge/dischargeefficiency and increased discharge capacity, as compared to those ofeach of the coin half-cells of Comparative Manufacture Examples 1 to 3.

Evaluation Example 7: Rate Capability Evaluation

Each of the coin half-cells of Manufacture Example 1 and ComparativeManufacture Examples 1 to 3 was charged at a constant current of 0.2 Cand a constant voltage of 4.3 V, the charging process was cut off at0.05 C, followed by resting for 10 minutes, and then each coin half-cellwas discharged at a constant current of 0.1 C until the voltage reached3.0 V. This cycle of charging and discharging was repeated 3 times.

At the 4th cycle, each coin half-cell was charged at a constant currentof 0.2 C and a constant voltage of 4.3 V, the charging process was cutoff at 0.05 C, followed by resting for 10 minutes, and then each coinhalf-cell was discharged at a constant current of 0.2 C until thevoltage reached 3.0 V.

At the 5th cycle, each coin half-cell was charged at a constant currentof 0.2 C and a constant voltage of 4.3 V, the charging process was cutoff at 0.05 C, followed by resting for 10 minutes, and then each coinhalf-cell was discharged at a constant current of 0.33 C until thevoltage reached 3.0 V.

At the 6th cycle, each coin half-cell was charged at a constant currentof 0.2 C and a constant voltage of 4.3 V, the charging process was cutoff at 0.05 C, followed by resting for 10 minutes, and then each coinhalf-cell was discharged at a constant current of 0.5 C until thevoltage reached 3.0 V.

At the 7th cycle, each coin half-cell was charged at a constant currentof 0.2 C and a constant voltage of 4.3 V, the charging process was cutoff at 0.05 C, followed by resting for 10 minutes, and then each coinhalf-cell was discharged at a constant current of 1.0 C until thevoltage reached 3.0 V.

At the 8th cycle, each coin half-cell was charged at a constant currentof 0.2 C and a constant voltage of 4.3 V, the charging process was cutoff at 0.05 C, followed by resting for 10 minutes, and then each coinhalf-cell was discharged at a constant current of 2.0 C until thevoltage reached 3.0 V.

At the 9th cycle, each coin half-cell was charged at a constant currentof 0.2 C and a constant voltage of 4.3 V, the charging process was cutoff at 0.05 C, followed by resting for 10 minutes, and then each coinhalf-cell was discharged at a constant current of 3.0 C until thevoltage reached 3.0 V.

The rate capability of each coin half-cell was calculated using Equation3 below.

Rate discharge capability (%)=[discharge capacity at 1 C/dischargecapacity at 0.1 C]×100  Equation 3

Some of the results of discharge capacity and high rate capability ateach cycle are shown in Table 6 below.

TABLE 6 Rate 0.2 C 0.5 C 1.0 C capability [mAh/g] [mAh/g] [mAh/g] [%]Manufacture Example 1 195.8 190.8 185.4 93.4 Comparative 194.4 187.4180.4 91.7 Manufacture Example 1 Comparative 183.7 177.8 170.2 91.1Manufacture Example 2 Comparative 194.7 187.9 180.9 91.5 ManufactureExample 3

Referring to Table 6, the coin half-cell of Manufacture Example 1exhibited enhanced discharge capacity and enhanced rate capability, ascompared to those of the coin half-cells of Comparative ManufactureExamples 1 to 3.

As is apparent from the foregoing description, by using a nickel-basedactive material precursor for a lithium secondary battery, according toembodiments of the present disclosure, a nickel-based active material inwhich deterioration due to cation mixing is suppressed or reduced andstructural stability is enhanced may be obtained. A lithium secondarybattery using such nickel-based active material as a positive activematerial exhibits enhanced capacity and enhanced lifespancharacteristics.

As used herein, the terms “use,” “using,” and “used” may be consideredsynonymous with the terms “utilize,” “utilizing,” and “utilized,”respectively.

In addition, the terms “substantially,” “about,” and similar terms areused as terms of approximation and not as terms of degree, and areintended to account for the inherent deviations in measured orcalculated values that would be recognized by those of ordinary skill inthe art.

Also, any numerical range recited herein is intended to include allsub-ranges of the same numerical precision subsumed within the recitedrange. For example, a range of “1.0 to 10.0” is intended to include allsubranges between (and including) the recited minimum value of 1.0 andthe recited maximum value of 10.0, that is, having a minimum value equalto or greater than 1.0 and a maximum value equal to or less than 10.0,such as, for example, 2.4 to 7.6. Any maximum numerical limitationrecited herein is intended to include all lower numerical limitationssubsumed therein and any minimum numerical limitation recited in thisspecification is intended to include all higher numerical limitationssubsumed therein. Accordingly, Applicant reserves the right to amendthis specification, including the claims, to expressly recite anysub-range subsumed within the ranges expressly recited herein.

It should be understood that embodiments described herein should beconsidered in a descriptive sense only and not for purposes oflimitation. Descriptions of features or aspects within each embodimentshould typically be considered as available for other similar featuresor aspects in other embodiments.

While one or more embodiments have been described with reference to thefigures, it will be understood by those of ordinary skill in the artthat various changes in form and details may be made therein withoutdeparting from the spirit and scope of the present disclosure as definedby the following claims and their equivalents.

What is claimed is:
 1. A nickel-based active material for a lithiumsecondary battery comprising a particulate structure comprising a coreportion, an intermediate layer portion on the core portion, and a shellportion on the intermediate layer portion, wherein the nickel-basedactive material comprises nickel (Ni), the intermediate layer portionand the shell portion comprise primary particles radially arranged onthe core portion, each of the core portion and the intermediate layerportion comprises a cation or anion different from that of the shellportion, the cation comprises at least one selected from boron (B),magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), titanium(Ti), vanadium (V), tungsten (W), chromium (Cr), iron (Fe), copper (Cu),zirconium (Zr), and aluminum (Al), and the anion comprises at least oneselected from phosphate (PO₄), BO₂, B₄O₇, B₃O₅, and F.
 2. Thenickel-based active material of claim 1, wherein the shell portioncomprises at least one cation selected from B, Mg, Ca, Sr, Ba, Ti, V, W,Cr, Fe, Cu, Zr, and Al.
 3. The nickel-based active material of claim 1,wherein a content of the cation is in a range of greater than about 0mol % to about 0.9 mol % with respect to a total amount of thenickel-based active material.
 4. The nickel-based active material ofclaim 1, wherein a content of the cation in the shell portion is in arange of greater than about 0 mol % to about 0.41 mol % with respect toa total amount of the nickel-based active material.
 5. The nickel-basedactive material of claim 1, wherein a content of the cation is in arange of greater than about 0 mol % to about 0.28 mol % with respect toa total amount of the nickel-based active material.
 6. The nickel-basedactive material of claim 1, wherein the core portion and theintermediate layer portion comprise at least one anion selected fromphosphate (PO₄), BO₂, B₄O₇, B₃O₅, and F.
 7. The nickel-based activematerial of claim 1, wherein a content of the anion is in a range ofgreater than about 0 mol % to 0.06 mol % with respect to a total amountof the nickel-based active material.
 8. The nickel-based active materialof claim 1, wherein a content of the cation in the shell portion is in arange of greater than about 0 mol % to about 2 mol % with respect to atotal amount of the nickel-based active material, and a content of theanion in each of the core portion and the intermediate layer portion isin a range of greater than about 0 mol % to about 1 mol % with respectto a total amount of the nickel-based active material.
 9. Thenickel-based active material of claim 1, wherein a content of the cationin the shell portion is in a range of greater than about 0 mol % toabout 1.33 mol % with respect to a total amount of the nickel-basedactive material, and a content of the anion in each of the core portionand the intermediate layer portion is in a range of greater than about 0mol % to about 0.18 mol % with respect to a total amount of thenickel-based active material.
 10. The nickel-based active material ofclaim 1, wherein porosity of the core portion, the intermediate layerportion, and the shell portion is sequentially reduced.
 11. Thenickel-based active material of claim 1, wherein the intermediate layerportion and the shell portion are each lower in porosity than the coreportion, or the core portion and the shell portion are each higher inporosity than the intermediate layer portion.
 12. The nickel-basedactive material of claim 1, wherein the nickel-based active material hasa mean particle diameter of about 9 μm to about 20 μm.
 13. Thenickel-based active material of claim 1, wherein the nickel-based activematerial comprises plate particles, and wherein major axes of the plateparticles are radially arranged.
 14. The nickel-based active material ofclaim 1, wherein the nickel-based active material is a compoundrepresented by Formula 3 or Formula 4:Li_(a)(Ni_(1-x-y-z)Co_(x)Mn_(y)M_(z))O_(2-α)X_(α)  Formula 3Li_(a)(Ni_(1-x-y-z)Co_(x)Al_(y)M_(z))O_(2-α)X_(α),  Formula 2 wherein,in Formulae 3 and 4, M is at least one element selected from B, Mg, Ca,Sr, Ba, Ti, V, W, Cr, Fe, Cu, Zr, and Al, X is at least one selectedfrom PO₄, BO₂, B₄O₇, B₃O₅, and F, 0.95≤a≤1.3, x≤(1-x-y-z), y≤(1-x-y-z),0<x<1, 0<y<1, 0<z≤0.01, and 0<α≤0.01.
 15. The nickel-based activematerial of claim 1, wherein a content of nickel in the nickel-basedactive material is in a range of about 33 mol % to about 97 mol % withrespect to a total amount of transition metals, and is higher than acontent of manganese or aluminium and a content of cobalt, and whereinthe transition metals are Ni, Co, and Mn in Formula 3, and are Ni, Co,and Al in Formula
 4. 16. The nickel-based active material of claim 1,wherein the nickel-based active material is one selected fromLi(Ni_(0.6)Co_(0.2)Mn_(0.2))_(1-a)M_(a)O_(2-α)X_(α),Li(Ni_(0.5)Co_(0.2)Mn_(0.3))_(1-a)M_(a)O_(2-α)X_(α),Li(Ni_(0.7)Co_(0.15)Mn_(0.15))_(1-a)M_(a)O_(2-α)X_(α),Li(Ni_(0.85)Co_(0.1)Al_(0.05))_(1-a)M_(a)O_(2-α)X_(α), orLi(Ni_(0.91)Co_(0.06)Mn_(0.03))_(1-a)M_(a)O_(2-α)X_(α), wherein 0<a<0.01and 0<α≤0.01, M is at least one element selected from B, Mg, Ca, Sr, Ba,Ti, V, W, Cr, Fe, Cu, Zr, and Al, and X is at least one selected fromPO₄, BO₂, B₄O₇, B₃O₅, and F.
 17. The nickel-based active material ofclaim 1, wherein the shell portion comprises open pores.
 18. A lithiumsecondary battery comprising: a positive electrode comprising thenickel-based active material of claim 1; a negative electrode; and anelectrolyte disposed between the positive electrode and the negativeelectrode.